diff --git a/Cargo.lock b/Cargo.lock
index bddde66f4..a323c86de 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1783,7 +1783,7 @@ dependencies = [
 [[package]]
 name = "milli"
 version = "0.19.0"
-source = "git+https://github.com/meilisearch/milli.git?tag=v0.19.0#d7943fe22553b8205b86c32a0f2656d9e42de351"
+source = "git+https://github.com/meilisearch/milli.git?branch=update-error-format#3599df77f05f4e89a28c0160411e95a840e0b227"
 dependencies = [
  "bimap",
  "bincode",
diff --git a/meilisearch-error/src/lib.rs b/meilisearch-error/src/lib.rs
index 3a3e2229a..8c9ee411c 100644
--- a/meilisearch-error/src/lib.rs
+++ b/meilisearch-error/src/lib.rs
@@ -62,6 +62,7 @@ pub enum Code {
 
     MaxFieldsLimitExceeded,
     MissingDocumentId,
+    InvalidDocumentId,
 
     Facet,
     Filter,
@@ -76,6 +77,7 @@ pub enum Code {
     InvalidToken,
     MissingAuthorizationHeader,
     NotFound,
+    TaskNotFound,
     PayloadTooLarge,
     RetrieveDocument,
     SearchDocuments,
@@ -99,7 +101,7 @@ impl Code {
             // index related errors
             // create index is thrown on internal error while creating an index.
             CreateIndex => ErrCode::internal("index_creation_failed", StatusCode::BAD_REQUEST),
-            IndexAlreadyExists => ErrCode::invalid("index_already_exists", StatusCode::BAD_REQUEST),
+            IndexAlreadyExists => ErrCode::invalid("index_already_exists", StatusCode::CONFLICT),
             // thrown when requesting an unexisting index
             IndexNotFound => ErrCode::invalid("index_not_found", StatusCode::NOT_FOUND),
             InvalidIndexUid => ErrCode::invalid("invalid_index_uid", StatusCode::BAD_REQUEST),
@@ -113,7 +115,7 @@ impl Code {
             MissingPrimaryKey => ErrCode::invalid("missing_primary_key", StatusCode::BAD_REQUEST),
             // error thrown when trying to set an already existing primary key
             PrimaryKeyAlreadyPresent => {
-                ErrCode::invalid("primary_key_already_present", StatusCode::BAD_REQUEST)
+                ErrCode::invalid("index_primary_key_already_exists", StatusCode::BAD_REQUEST)
             }
             // invalid ranking rule
             InvalidRankingRule => ErrCode::invalid("invalid_request", StatusCode::BAD_REQUEST),
@@ -123,6 +125,7 @@ impl Code {
                 ErrCode::invalid("max_fields_limit_exceeded", StatusCode::BAD_REQUEST)
             }
             MissingDocumentId => ErrCode::invalid("missing_document_id", StatusCode::BAD_REQUEST),
+            InvalidDocumentId => ErrCode::invalid("invalid_document_id", StatusCode::BAD_REQUEST),
 
             // error related to facets
             Facet => ErrCode::invalid("invalid_facet", StatusCode::BAD_REQUEST),
@@ -142,6 +145,7 @@ impl Code {
             MissingAuthorizationHeader => {
                 ErrCode::authentication("missing_authorization_header", StatusCode::UNAUTHORIZED)
             }
+            TaskNotFound => ErrCode::invalid("task_not_found", StatusCode::NOT_FOUND),
             NotFound => ErrCode::invalid("not_found", StatusCode::NOT_FOUND),
             PayloadTooLarge => ErrCode::invalid("payload_too_large", StatusCode::PAYLOAD_TOO_LARGE),
             RetrieveDocument => {
diff --git a/meilisearch-http/src/error.rs b/meilisearch-http/src/error.rs
index c3c8d5785..39dace4fc 100644
--- a/meilisearch-http/src/error.rs
+++ b/meilisearch-http/src/error.rs
@@ -12,11 +12,11 @@ use serde::{Deserialize, Serialize};
 #[derive(Debug, thiserror::Error)]
 pub enum MeilisearchHttpError {
     #[error("A Content-Type header is missing. Accepted values for the Content-Type header are: {}",
-            .0.iter().map(|s| format!("\"{}\"", s)).collect::<Vec<_>>().join(", "))]
+            .0.iter().map(|s| format!("`{}`", s)).collect::<Vec<_>>().join(", "))]
     MissingContentType(Vec<String>),
     #[error(
-        "The Content-Type \"{0}\" is invalid. Accepted values for the Content-Type header are: {}",
-        .1.iter().map(|s| format!("\"{}\"", s)).collect::<Vec<_>>().join(", ")
+        "The Content-Type `{0}` is invalid. Accepted values for the Content-Type header are: {}",
+        .1.iter().map(|s| format!("`{}`", s)).collect::<Vec<_>>().join(", ")
     )]
     InvalidContentType(String, Vec<String>),
 }
diff --git a/meilisearch-http/tests/common/index.rs b/meilisearch-http/tests/common/index.rs
index cb790ba70..2e126e67d 100644
--- a/meilisearch-http/tests/common/index.rs
+++ b/meilisearch-http/tests/common/index.rs
@@ -99,7 +99,7 @@ impl Index<'_> {
     pub async fn wait_update_id(&self, update_id: u64) -> Value {
         // try 10 times to get status, or panic to not wait forever
         let url = format!("/indexes/{}/updates/{}", self.uid, update_id);
-        for _ in 0..10 {
+        for _ in 0..20 {
             let (response, status_code) = self.service.get(&url).await;
             assert_eq!(status_code, 200, "response: {}", response);
 
diff --git a/meilisearch-http/tests/documents/add_documents.rs b/meilisearch-http/tests/documents/add_documents.rs
index 14f5c6dee..eaeabe417 100644
--- a/meilisearch-http/tests/documents/add_documents.rs
+++ b/meilisearch-http/tests/documents/add_documents.rs
@@ -80,7 +80,7 @@ async fn error_add_documents_test_bad_content_types() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The Content-Type "text/plain" is invalid. Accepted values for the Content-Type header are: "application/json", "application/x-ndjson", "text/csv""#
+            r#"The Content-Type `text/plain` is invalid. Accepted values for the Content-Type header are: `application/json`, `application/x-ndjson`, `text/csv`"#
         )
     );
     assert_eq!(response["code"], "invalid_content_type");
@@ -104,7 +104,7 @@ async fn error_add_documents_test_bad_content_types() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The Content-Type "text/plain" is invalid. Accepted values for the Content-Type header are: "application/json", "application/x-ndjson", "text/csv""#
+            r#"The Content-Type `text/plain` is invalid. Accepted values for the Content-Type header are: `application/json`, `application/x-ndjson`, `text/csv`"#
         )
     );
     assert_eq!(response["code"], "invalid_content_type");
@@ -145,7 +145,7 @@ async fn error_add_documents_test_no_content_type() {
     assert_eq!(
         response["message"],
         json!(
-            r#"A Content-Type header is missing. Accepted values for the Content-Type header are: "application/json", "application/x-ndjson", "text/csv""#
+            r#"A Content-Type header is missing. Accepted values for the Content-Type header are: `application/json`, `application/x-ndjson`, `text/csv`"#
         )
     );
     assert_eq!(response["code"], "missing_content_type");
@@ -168,7 +168,7 @@ async fn error_add_documents_test_no_content_type() {
     assert_eq!(
         response["message"],
         json!(
-            r#"A Content-Type header is missing. Accepted values for the Content-Type header are: "application/json", "application/x-ndjson", "text/csv""#
+            r#"A Content-Type header is missing. Accepted values for the Content-Type header are: `application/json`, `application/x-ndjson`, `text/csv`"#
         )
     );
     assert_eq!(response["code"], "missing_content_type");
@@ -204,7 +204,7 @@ async fn error_add_malformed_csv_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The csv payload provided is malformed. CSV error: record 1 (line: 2, byte: 12): found record with 3 fields, but the previous record has 2 fields."#
+            r#"The `csv` payload provided is malformed. `CSV error: record 1 (line: 2, byte: 12): found record with 3 fields, but the previous record has 2 fields`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -228,7 +228,7 @@ async fn error_add_malformed_csv_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The csv payload provided is malformed. CSV error: record 1 (line: 2, byte: 12): found record with 3 fields, but the previous record has 2 fields."#
+            r#"The `csv` payload provided is malformed. `CSV error: record 1 (line: 2, byte: 12): found record with 3 fields, but the previous record has 2 fields`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -264,7 +264,7 @@ async fn error_add_malformed_json_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The json payload provided is malformed. key must be a string at line 1 column 14."#
+            r#"The `json` payload provided is malformed. `Couldn't serialize document value: key must be a string at line 1 column 14`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -288,7 +288,7 @@ async fn error_add_malformed_json_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The json payload provided is malformed. key must be a string at line 1 column 14."#
+            r#"The `json` payload provided is malformed. `Couldn't serialize document value: key must be a string at line 1 column 14`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -324,7 +324,7 @@ async fn error_add_malformed_ndjson_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The ndjson payload provided is malformed. key must be a string at line 2 column 2."#
+            r#"The `ndjson` payload provided is malformed. `Couldn't serialize document value: key must be a string at line 1 column 2`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -348,7 +348,7 @@ async fn error_add_malformed_ndjson_documents() {
     assert_eq!(
         response["message"],
         json!(
-            r#"The ndjson payload provided is malformed. key must be a string at line 2 column 2."#
+            r#"The `ndjson` payload provided is malformed. `Couldn't serialize document value: key must be a string at line 1 column 2`."#
         )
     );
     assert_eq!(response["code"], json!("malformed_payload"));
@@ -359,6 +359,162 @@ async fn error_add_malformed_ndjson_documents() {
     );
 }
 
+#[actix_rt::test]
+async fn error_add_missing_payload_csv_documents() {
+    let document = "";
+
+    let server = Server::new().await;
+    let app = test::init_service(create_app!(
+        &server.service.meilisearch,
+        true,
+        &server.service.options
+    ))
+    .await;
+    // post
+    let req = test::TestRequest::post()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "text/csv"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(response["message"], json!(r#"A csv payload is missing."#));
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+
+    // put
+    let req = test::TestRequest::put()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "text/csv"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(response["message"], json!(r#"A csv payload is missing."#));
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+}
+
+#[actix_rt::test]
+async fn error_add_missing_payload_json_documents() {
+    let document = "";
+
+    let server = Server::new().await;
+    let app = test::init_service(create_app!(
+        &server.service.meilisearch,
+        true,
+        &server.service.options
+    ))
+    .await;
+    // post
+    let req = test::TestRequest::post()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "application/json"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(response["message"], json!(r#"A json payload is missing."#));
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+
+    // put
+    let req = test::TestRequest::put()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "application/json"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(response["message"], json!(r#"A json payload is missing."#));
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+}
+
+#[actix_rt::test]
+async fn error_add_missing_payload_ndjson_documents() {
+    let document = "";
+
+    let server = Server::new().await;
+    let app = test::init_service(create_app!(
+        &server.service.meilisearch,
+        true,
+        &server.service.options
+    ))
+    .await;
+    // post
+    let req = test::TestRequest::post()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "application/x-ndjson"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(
+        response["message"],
+        json!(r#"A ndjson payload is missing."#)
+    );
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+
+    // put
+    let req = test::TestRequest::put()
+        .uri("/indexes/dog/documents")
+        .set_payload(document.to_string())
+        .insert_header(("content-type", "application/x-ndjson"))
+        .to_request();
+    let res = test::call_service(&app, req).await;
+    let status_code = res.status();
+    let body = test::read_body(res).await;
+    let response: Value = serde_json::from_slice(&body).unwrap_or_default();
+    assert_eq!(status_code, 400);
+    assert_eq!(
+        response["message"],
+        json!(r#"A ndjson payload is missing."#)
+    );
+    assert_eq!(response["code"], json!("missing_payload"));
+    assert_eq!(response["type"], json!("invalid_request"));
+    assert_eq!(
+        response["link"],
+        json!("https://docs.meilisearch.com/errors#missing_payload")
+    );
+}
+
 #[actix_rt::test]
 async fn add_documents_no_index_creation() {
     let server = Server::new().await;
@@ -411,7 +567,7 @@ async fn error_document_add_create_index_bad_uid() {
     let (response, code) = index.add_documents(json!([]), None).await;
 
     let expected_response = json!({
-        "message": "883  fj! is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
+        "message": "`883  fj!` is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
         "code": "invalid_index_uid",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_index_uid"
@@ -428,7 +584,7 @@ async fn error_document_update_create_index_bad_uid() {
     let (response, code) = index.update_documents(json!([]), None).await;
 
     let expected_response = json!({
-        "message": "883  fj! is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
+        "message": "`883  fj!` is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
         "code": "invalid_index_uid",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_index_uid"
@@ -646,13 +802,13 @@ async fn error_add_documents_bad_document_id() {
     index.wait_update_id(0).await;
     let (response, code) = index.get_update(0).await;
     assert_eq!(code, 200);
-    assert_eq!(response["status"], "failed");
-    assert_eq!(response["message"], "Document identifier foo & bar is invalid. A document identifier can be of type integer or string, only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and underscores (_).");
-    assert_eq!(response["code"], "invalid_document_id");
-    assert_eq!(response["type"], "invalid_request");
+    assert_eq!(response["status"], json!("failed"));
+    assert_eq!(response["message"], json!("Document identifier `foo & bar` is invalid. A document identifier can be of type integer or string, only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and underscores (_)."));
+    assert_eq!(response["code"], json!("invalid_document_id"));
+    assert_eq!(response["type"], json!("invalid_request"));
     assert_eq!(
         response["link"],
-        "https://docs.meilisearch.com/errors#invalid_document_id"
+        json!("https://docs.meilisearch.com/errors#invalid_document_id")
     );
 }
 
@@ -671,13 +827,13 @@ async fn error_update_documents_bad_document_id() {
     index.wait_update_id(0).await;
     let (response, code) = index.get_update(0).await;
     assert_eq!(code, 200);
-    assert_eq!(response["status"], "failed");
-    assert_eq!(response["message"], "Document identifier foo & bar is invalid. A document identifier can be of type integer or string, only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and underscores (_).");
-    assert_eq!(response["code"], "invalid_document_id");
-    assert_eq!(response["type"], "invalid_request");
+    assert_eq!(response["status"], json!("failed"));
+    assert_eq!(response["message"], json!("Document identifier `foo & bar` is invalid. A document identifier can be of type integer or string, only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and underscores (_)."));
+    assert_eq!(response["code"], json!("invalid_document_id"));
+    assert_eq!(response["type"], json!("invalid_request"));
     assert_eq!(
         response["link"],
-        "https://docs.meilisearch.com/errors#invalid_document_id"
+        json!("https://docs.meilisearch.com/errors#invalid_document_id")
     );
 }
 
@@ -699,13 +855,13 @@ async fn error_add_documents_missing_document_id() {
     assert_eq!(response["status"], "failed");
     assert_eq!(
         response["message"],
-        r#"Document doesn't have a docid attribute: {"id":"11","content":"foobar"}."#
+        json!(r#"Document doesn't have a `docid` attribute: `{"id":"11","content":"foobar"}`."#)
     );
-    assert_eq!(response["code"], "missing_document_id");
-    assert_eq!(response["type"], "invalid_request");
+    assert_eq!(response["code"], json!("missing_document_id"));
+    assert_eq!(response["type"], json!("invalid_request"));
     assert_eq!(
         response["link"],
-        "https://docs.meilisearch.com/errors#missing_document_id"
+        json!("https://docs.meilisearch.com/errors#missing_document_id")
     );
 }
 
@@ -727,7 +883,7 @@ async fn error_update_documents_missing_document_id() {
     assert_eq!(response["status"], "failed");
     assert_eq!(
         response["message"],
-        r#"Document doesn't have a docid attribute: {"id":"11","content":"foobar"}."#
+        r#"Document doesn't have a `docid` attribute: `{"id":"11","content":"foobar"}`."#
     );
     assert_eq!(response["code"], "missing_document_id");
     assert_eq!(response["type"], "invalid_request");
@@ -737,109 +893,41 @@ async fn error_update_documents_missing_document_id() {
     );
 }
 
-#[actix_rt::test]
-async fn error_add_documents_with_primary_key_and_primary_key_already_exists() {
-    let server = Server::new().await;
-    let index = server.index("test");
+// #[actix_rt::test]
+// async fn error_document_field_limit_reached() {
+//     let server = Server::new().await;
+//     let index = server.index("test");
 
-    index.create(Some("primary")).await;
-    let documents = json!([
-        {
-            "id": 1,
-            "content": "foo",
-        }
-    ]);
+//     index.create(Some("id")).await;
 
-    let (_response, code) = index.add_documents(documents, Some("id")).await;
-    assert_eq!(code, 202);
+//     let mut big_object = std::collections::HashMap::new();
+//     big_object.insert("id".to_owned(), "wow");
+//     for i in 0..65535 {
+//         let key = i.to_string();
+//         big_object.insert(key, "I am a text!");
+//     }
 
-    index.wait_update_id(0).await;
+//     let documents = json!([big_object]);
 
-    let (response, code) = index.get_update(0).await;
-    assert_eq!(code, 200);
-    assert_eq!(response["status"], "failed");
-    assert_eq!(response["message"], "Index test already has a primary key.");
-    assert_eq!(response["code"], "index_primary_key_already_exists");
-    assert_eq!(response["type"], "invalid_request");
-    assert_eq!(
-        response["link"],
-        "https://docs.meilisearch.com/errors#index_primary_key_already_exists"
-    );
+//     let (_response, code) = index.update_documents(documents, Some("id")).await;
+//     assert_eq!(code, 202);
 
-    let (response, code) = index.get().await;
-    assert_eq!(code, 200);
-    assert_eq!(response["primaryKey"], "primary");
-}
-
-#[actix_rt::test]
-async fn error_update_documents_with_primary_key_and_primary_key_already_exists() {
-    let server = Server::new().await;
-    let index = server.index("test");
-
-    index.create(Some("primary")).await;
-    let documents = json!([
-        {
-            "id": 1,
-            "content": "foo",
-        }
-    ]);
-
-    let (_response, code) = index.update_documents(documents, Some("id")).await;
-    assert_eq!(code, 202);
-
-    index.wait_update_id(0).await;
-    let (response, code) = index.get_update(0).await;
-    assert_eq!(code, 200);
-    // Documents without a primary key are not accepted.
-    assert_eq!(response["status"], "failed");
-    assert_eq!(response["message"], "Index test already has a primary key.");
-    assert_eq!(response["code"], "index_primary_key_already_exists");
-    assert_eq!(response["type"], "invalid_request");
-    assert_eq!(
-        response["link"],
-        "https://docs.meilisearch.com/errors#index_primary_key_already_exists"
-    );
-
-    let (response, code) = index.get().await;
-    assert_eq!(code, 200);
-    assert_eq!(response["primaryKey"], "primary");
-}
-
-#[actix_rt::test]
-async fn error_document_field_limit_reached() {
-    let server = Server::new().await;
-    let index = server.index("test");
-
-    index.create(Some("id")).await;
-
-    let mut big_object = std::collections::HashMap::new();
-    big_object.insert("id".to_owned(), "wow");
-    for i in 0..65535 {
-        let key = i.to_string();
-        big_object.insert(key, "I am a text!");
-    }
-
-    let documents = json!([big_object]);
-
-    let (_response, code) = index.update_documents(documents, Some("id")).await;
-    assert_eq!(code, 202);
-
-    index.wait_update_id(0).await;
-    let (response, code) = index.get_update(0).await;
-    assert_eq!(code, 200);
-    // Documents without a primary key are not accepted.
-    assert_eq!(response["status"], "failed");
-    assert_eq!(
-        response["message"],
-        "A document cannot contain more than 65,535 fields."
-    );
-    assert_eq!(response["code"], "document_fields_limit_reached");
-    assert_eq!(response["type"], "invalid_request");
-    assert_eq!(
-        response["link"],
-        "https://docs.meilisearch.com/errors#document_fields_limit_reached"
-    );
-}
+//     index.wait_update_id(0).await;
+//     let (response, code) = index.get_update(0).await;
+//     assert_eq!(code, 200);
+//     // Documents without a primary key are not accepted.
+//     assert_eq!(response["status"], "failed");
+//     assert_eq!(
+//         response["message"],
+//         "A document cannot contain more than 65,535 fields."
+//     );
+//     assert_eq!(response["code"], "document_fields_limit_reached");
+//     assert_eq!(response["type"], "invalid_request");
+//     assert_eq!(
+//         response["link"],
+//         "https://docs.meilisearch.com/errors#document_fields_limit_reached"
+//     );
+// }
 
 #[actix_rt::test]
 async fn error_add_documents_invalid_geo_field() {
@@ -885,7 +973,7 @@ async fn error_add_documents_payload_size() {
     let (response, code) = index.add_documents(documents, None).await;
 
     let expected_response = json!({
-        "message": "The payload cannot exceed 10MB.",
+        "message": "The provided payload reached the size limit.",
         "code": "payload_too_large",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#payload_too_large"
diff --git a/meilisearch-http/tests/documents/delete_documents.rs b/meilisearch-http/tests/documents/delete_documents.rs
index 81125e580..56210059b 100644
--- a/meilisearch-http/tests/documents/delete_documents.rs
+++ b/meilisearch-http/tests/documents/delete_documents.rs
@@ -87,7 +87,7 @@ async fn error_delete_batch_unexisting_index() {
     let server = Server::new().await;
     let (response, code) = server.index("test").delete_batch(vec![]).await;
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/documents/get_documents.rs b/meilisearch-http/tests/documents/get_documents.rs
index 11f43f2c4..6d9a2d150 100644
--- a/meilisearch-http/tests/documents/get_documents.rs
+++ b/meilisearch-http/tests/documents/get_documents.rs
@@ -20,7 +20,7 @@ async fn error_get_unexisting_document() {
     let (response, code) = index.get_document(1, None).await;
 
     let expected_response = json!({
-        "message": "Document 1 not found.",
+        "message": "Document `1` not found.",
         "code": "document_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#document_not_found"
@@ -64,7 +64,7 @@ async fn error_get_unexisting_index_all_documents() {
         .await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/index/create_index.rs b/meilisearch-http/tests/index/create_index.rs
index e5cfa2fa5..2d001517f 100644
--- a/meilisearch-http/tests/index/create_index.rs
+++ b/meilisearch-http/tests/index/create_index.rs
@@ -78,7 +78,7 @@ async fn error_create_existing_index() {
     let (response, code) = index.create(Some("primary")).await;
 
     let expected_response = json!({
-        "message": "Index primary already exists.",
+        "message": "Index `test` already exists.",
         "code": "index_already_exists",
         "type": "invalid_request",
         "link":"https://docs.meilisearch.com/errors#index_already_exists"
@@ -95,7 +95,7 @@ async fn error_create_with_invalid_index_uid() {
     let (response, code) = index.create(None).await;
 
     let expected_response = json!({
-        "message": "test test#! is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
+        "message": "`test test#!` is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).",
         "code": "invalid_index_uid",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_index_uid"
diff --git a/meilisearch-http/tests/index/delete_index.rs b/meilisearch-http/tests/index/delete_index.rs
index 84c780650..c4366af35 100644
--- a/meilisearch-http/tests/index/delete_index.rs
+++ b/meilisearch-http/tests/index/delete_index.rs
@@ -24,7 +24,7 @@ async fn error_delete_unexisting_index() {
     let (response, code) = index.delete().await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/index/get_index.rs b/meilisearch-http/tests/index/get_index.rs
index ec35ea283..4a1fa6692 100644
--- a/meilisearch-http/tests/index/get_index.rs
+++ b/meilisearch-http/tests/index/get_index.rs
@@ -30,7 +30,7 @@ async fn error_get_unexisting_index() {
     let (response, code) = index.get().await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/index/stats.rs b/meilisearch-http/tests/index/stats.rs
index 7abbd0cd4..755366fed 100644
--- a/meilisearch-http/tests/index/stats.rs
+++ b/meilisearch-http/tests/index/stats.rs
@@ -53,7 +53,7 @@ async fn error_get_stats_unexisting_index() {
     let (response, code) = server.index("test").stats().await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/index/update_index.rs b/meilisearch-http/tests/index/update_index.rs
index 5d92a0a16..a22def409 100644
--- a/meilisearch-http/tests/index/update_index.rs
+++ b/meilisearch-http/tests/index/update_index.rs
@@ -44,14 +44,23 @@ async fn update_nothing() {
 async fn error_update_existing_primary_key() {
     let server = Server::new().await;
     let index = server.index("test");
-    let (_response, code) = index.create(Some("primary")).await;
+    let (_response, code) = index.create(Some("id")).await;
 
     assert_eq!(code, 201);
 
-    let (response, code) = index.update(Some("primary2")).await;
+    let documents = json!([
+        {
+            "id": "11",
+            "content": "foobar"
+        }
+    ]);
+    index.add_documents(documents, None).await;
+    index.wait_update_id(0).await;
+
+    let (response, code) = index.update(Some("primary")).await;
 
     let expected_response = json!({
-        "message": "Index test already has a primary key.",
+        "message": "Index already has a primary key: `id`.",
         "code": "index_primary_key_already_exists",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_primary_key_already_exists"
@@ -67,7 +76,7 @@ async fn error_update_unexisting_index() {
     let (response, code) = server.index("test").update(None).await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-http/tests/search/errors.rs b/meilisearch-http/tests/search/errors.rs
index d7e4b342e..e4dc12f40 100644
--- a/meilisearch-http/tests/search/errors.rs
+++ b/meilisearch-http/tests/search/errors.rs
@@ -8,10 +8,17 @@ async fn search_unexisting_index() {
     let server = Server::new().await;
     let index = server.index("test");
 
+    let expected_response = json!({
+        "message": "Index `test` not found.",
+        "code": "index_not_found",
+        "type": "invalid_request",
+        "link": "https://docs.meilisearch.com/errors#index_not_found"
+    });
+
     index
         .search(json!({"q": "hello"}), |response, code| {
-            assert_eq!(code, 404, "{}", response);
-            assert_eq!(response["errorCode"], "index_not_found");
+            assert_eq!(code, 404);
+            assert_eq!(response, expected_response);
         })
         .await;
 }
@@ -24,7 +31,7 @@ async fn search_unexisting_parameter() {
     index
         .search(json!({"marin": "hello"}), |response, code| {
             assert_eq!(code, 400, "{}", response);
-            assert_eq!(response["errorCode"], "bad_request");
+            assert_eq!(response["code"], "bad_request");
         })
         .await;
 }
@@ -43,13 +50,13 @@ async fn filter_invalid_syntax_object() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Invalid syntax for the filter parameter: :syntaxErrorHelper:REPLACE_ME.",
+        "message": "Invalid syntax for the filter parameter: ` --> 1:7\n  |\n1 | title & Glass\n  |       ^---\n  |\n  = expected word`.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
     });
     index
-        .search(json!({"filter": {"title": "Glass"}}), |response, code| {
+        .search(json!({"filter": "title & Glass"}), |response, code| {
             assert_eq!(response, expected_response);
             assert_eq!(code, 400);
         })
@@ -70,19 +77,16 @@ async fn filter_invalid_syntax_array() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Invalid syntax for the filter parameter: :syntaxErrorHelper:REPLACE_ME.",
+        "message": "Invalid syntax for the filter parameter: ` --> 1:7\n  |\n1 | title & Glass\n  |       ^---\n  |\n  = expected word`.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
     });
     index
-        .search(
-            json!({"filter": [[["title = Glass"]]]}),
-            |response, code| {
-                assert_eq!(response, expected_response);
-                assert_eq!(code, 400);
-            },
-        )
+        .search(json!({"filter": [["title & Glass"]]}), |response, code| {
+            assert_eq!(response, expected_response);
+            assert_eq!(code, 400);
+        })
         .await;
 }
 
@@ -100,7 +104,7 @@ async fn filter_invalid_syntax_string() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Invalid syntax for the filter parameter: :syntaxErrorHelper:REPLACE_ME.",
+        "message": "Invalid syntax for the filter parameter: ` --> 1:15\n  |\n1 | title = Glass XOR title = Glass\n  |               ^---\n  |\n  = expected EOI, and, or or`.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -130,7 +134,7 @@ async fn filter_invalid_attribute_array() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Attribute many is not filterable. Available filterable attributes are: title.",
+        "message": "Attribute `many` is not filterable. Available filterable attributes are: `title`.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -157,7 +161,7 @@ async fn filter_invalid_attribute_string() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Attribute many is not filterable. Available filterable attributes are: title.",
+        "message": "Attribute `many` is not filterable. Available filterable attributes are: `title`.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -184,7 +188,7 @@ async fn filter_reserved_geo_attribute_array() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geo is a reserved keyword and thus can't be used as a filter expression. Use the _geoRadius(latitude, longitude, distance) built-in rule to filter on _geo field coordinates.",
+        "message": "`_geo` is a reserved keyword and thus can't be used as a filter expression. Use the _geoRadius(latitude, longitude, distance) built-in rule to filter on _geo field coordinates.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -211,7 +215,7 @@ async fn filter_reserved_geo_attribute_string() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geo is a reserved keyword and thus can't be used as a filter expression. Use the _geoRadius(latitude, longitude, distance) built-in rule to filter on _geo field coordinates.",
+        "message": "`_geo` is a reserved keyword and thus can't be used as a filter expression. Use the _geoRadius(latitude, longitude, distance) built-in rule to filter on _geo field coordinates.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -238,7 +242,7 @@ async fn filter_reserved_attribute_array() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geoDistance is a reserved keyword and thus can't be used as a filter expression.",
+        "message": "`_geoDistance` is a reserved keyword and thus can't be used as a filter expression.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -268,7 +272,7 @@ async fn filter_reserved_attribute_string() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geoDistance is a reserved keyword and thus can't be used as a filter expression.",
+        "message": "`_geoDistance` is a reserved keyword and thus can't be used as a filter expression.",
         "code": "invalid_filter",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_filter"
@@ -298,7 +302,7 @@ async fn sort_geo_reserved_attribute() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geo is a reserved keyword and thus can't be used as a filter expression. Use the _geoPoint(latitude, longitude) built-in rule to sort on _geo field coordinates.",
+        "message": "`_geo` is a reserved keyword and thus can't be used as a sort expression. Use the _geoPoint(latitude, longitude) built-in rule to sort on _geo field coordinates.",
         "code": "invalid_sort",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_sort"
@@ -330,7 +334,7 @@ async fn sort_reserved_attribute() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "_geoDistance is a reserved keyword and thus can't be used as a filter expression.",
+        "message": "`_geoDistance` is a reserved keyword and thus can't be used as a sort expression.",
         "code": "invalid_sort",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_sort"
@@ -362,7 +366,7 @@ async fn sort_unsortable_attribute() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Attribute title is not sortable. Available sortable attributes are: id.",
+        "message": "Attribute `title` is not sortable. Available sortable attributes are: `id`.",
         "code": "invalid_sort",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_sort"
@@ -394,7 +398,7 @@ async fn sort_invalid_syntax() {
     index.wait_update_id(1).await;
 
     let expected_response = json!({
-        "message": "Invalid syntax for the sort parameter: :syntaxErrorHelper:REPLACE_ME.",
+        "message": "Invalid syntax for the sort parameter: expected expression ending by `:asc` or `:desc`, found `title`.",
         "code": "invalid_sort",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#invalid_sort"
@@ -419,7 +423,7 @@ async fn sort_unset_ranking_rule() {
 
     index
         .update_settings(
-            json!({"sortableAttributes": ["id"], "rankingRules": ["proximity", "exactness"]}),
+            json!({"sortableAttributes": ["title"], "rankingRules": ["proximity", "exactness"]}),
         )
         .await;
 
@@ -436,7 +440,7 @@ async fn sort_unset_ranking_rule() {
     index
         .search(
             json!({
-                "sort": ["title"]
+                "sort": ["title:asc"]
             }),
             |response, code| {
                 assert_eq!(response, expected_response);
diff --git a/meilisearch-http/tests/updates/mod.rs b/meilisearch-http/tests/updates/mod.rs
index c4ab1a275..f7bf9450a 100644
--- a/meilisearch-http/tests/updates/mod.rs
+++ b/meilisearch-http/tests/updates/mod.rs
@@ -7,7 +7,7 @@ async fn error_get_update_unexisting_index() {
     let (response, code) = server.index("test").get_update(0).await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
@@ -25,7 +25,7 @@ async fn error_get_unexisting_update_status() {
     let (response, code) = index.get_update(0).await;
 
     let expected_response = json!({
-        "message": "Task 0 not found.",
+        "message": "Task `0` not found.",
         "code": "task_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#task_not_found"
@@ -60,7 +60,7 @@ async fn error_list_updates_unexisting_index() {
     let (response, code) = server.index("test").list_updates().await;
 
     let expected_response = json!({
-        "message": "Index test not found.",
+        "message": "Index `test` not found.",
         "code": "index_not_found",
         "type": "invalid_request",
         "link": "https://docs.meilisearch.com/errors#index_not_found"
diff --git a/meilisearch-lib/Cargo.toml b/meilisearch-lib/Cargo.toml
index 429481539..74592419b 100644
--- a/meilisearch-lib/Cargo.toml
+++ b/meilisearch-lib/Cargo.toml
@@ -30,7 +30,7 @@ lazy_static = "1.4.0"
 log = "0.4.14"
 meilisearch-error = { path = "../meilisearch-error" }
 meilisearch-tokenizer = { git = "https://github.com/meilisearch/tokenizer.git", tag = "v0.2.5" }
-milli = { git = "https://github.com/meilisearch/milli.git", tag = "v0.19.0" }
+milli = { git = "https://github.com/meilisearch/milli.git", branch = "update-error-format" }
 mime = "0.3.16"
 num_cpus = "1.13.0"
 once_cell = "1.8.0"
diff --git a/meilisearch-lib/src/document_formats.rs b/meilisearch-lib/src/document_formats.rs
index 1d965d260..9ddbdf09d 100644
--- a/meilisearch-lib/src/document_formats.rs
+++ b/meilisearch-lib/src/document_formats.rs
@@ -25,9 +25,9 @@ impl fmt::Display for PayloadType {
 
 #[derive(thiserror::Error, Debug)]
 pub enum DocumentFormatError {
-    #[error("Internal error: {0}")]
+    #[error("Internal error!: {0}")]
     Internal(Box<dyn std::error::Error + Send + Sync + 'static>),
-    #[error("The {1} payload provided is malformed. {0}.")]
+    #[error("The `{1}` payload provided is malformed. `{0}`.")]
     MalformedPayload(
         Box<dyn std::error::Error + Send + Sync + 'static>,
         PayloadType,
@@ -55,18 +55,18 @@ impl ErrorCode for DocumentFormatError {
 internal_error!(DocumentFormatError: io::Error);
 
 /// reads csv from input and write an obkv batch to writer.
-pub fn read_csv(input: impl Read, writer: impl Write + Seek) -> Result<()> {
+pub fn read_csv(input: impl Read, writer: impl Write + Seek) -> Result<usize> {
     let writer = BufWriter::new(writer);
-    DocumentBatchBuilder::from_csv(input, writer)
-        .map_err(|e| (PayloadType::Csv, e))?
-        .finish()
-        .map_err(|e| (PayloadType::Csv, e))?;
+    let builder =
+        DocumentBatchBuilder::from_csv(input, writer).map_err(|e| (PayloadType::Csv, e))?;
+    let document_count = builder.len();
+    builder.finish().map_err(|e| (PayloadType::Csv, e))?;
 
-    Ok(())
+    Ok(document_count)
 }
 
 /// reads jsonl from input and write an obkv batch to writer.
-pub fn read_ndjson(input: impl Read, writer: impl Write + Seek) -> Result<()> {
+pub fn read_ndjson(input: impl Read, writer: impl Write + Seek) -> Result<usize> {
     let mut reader = BufReader::new(input);
     let writer = BufWriter::new(writer);
 
@@ -80,19 +80,22 @@ pub fn read_ndjson(input: impl Read, writer: impl Write + Seek) -> Result<()> {
         buf.clear();
     }
 
+    let document_count = builder.len();
+
     builder.finish().map_err(|e| (PayloadType::Ndjson, e))?;
 
-    Ok(())
+    Ok(document_count)
 }
 
 /// reads json from input and write an obkv batch to writer.
-pub fn read_json(input: impl Read, writer: impl Write + Seek) -> Result<()> {
+pub fn read_json(input: impl Read, writer: impl Write + Seek) -> Result<usize> {
     let writer = BufWriter::new(writer);
     let mut builder = DocumentBatchBuilder::new(writer).map_err(|e| (PayloadType::Json, e))?;
     builder
         .extend_from_json(input)
         .map_err(|e| (PayloadType::Json, e))?;
+    let document_count = builder.len();
     builder.finish().map_err(|e| (PayloadType::Json, e))?;
 
-    Ok(())
+    Ok(document_count)
 }
diff --git a/meilisearch-lib/src/error.rs b/meilisearch-lib/src/error.rs
index d29c18d25..689a8ddae 100644
--- a/meilisearch-lib/src/error.rs
+++ b/meilisearch-lib/src/error.rs
@@ -37,19 +37,17 @@ impl ErrorCode for MilliError<'_> {
                     // TODO: wait for spec for new error codes.
                     UserError::SerdeJson(_)
                     | UserError::MaxDatabaseSizeReached
-                    | UserError::InvalidDocumentId { .. }
                     | UserError::InvalidStoreFile
                     | UserError::NoSpaceLeftOnDevice
-                    | UserError::DocumentLimitReached => Code::Internal,
+                    | UserError::DocumentLimitReached
+                    | UserError::UnknownInternalDocumentId { .. } => Code::Internal,
                     UserError::AttributeLimitReached => Code::MaxFieldsLimitExceeded,
                     UserError::InvalidFilter(_) => Code::Filter,
-                    UserError::InvalidFilterAttribute(_) => Code::Filter,
                     UserError::MissingDocumentId { .. } => Code::MissingDocumentId,
+                    UserError::InvalidDocumentId { .. } => Code::InvalidDocumentId,
                     UserError::MissingPrimaryKey => Code::MissingPrimaryKey,
-                    UserError::PrimaryKeyCannotBeChanged => Code::PrimaryKeyAlreadyPresent,
-                    UserError::PrimaryKeyCannotBeReset => Code::PrimaryKeyAlreadyPresent,
+                    UserError::PrimaryKeyCannotBeChanged(_) => Code::PrimaryKeyAlreadyPresent,
                     UserError::SortRankingRuleMissing => Code::Sort,
-                    UserError::UnknownInternalDocumentId { .. } => Code::DocumentNotFound,
                     UserError::InvalidFacetsDistribution { .. } => Code::BadRequest,
                     UserError::InvalidSortableAttribute { .. } => Code::Sort,
                     UserError::CriterionError(_) => Code::InvalidRankingRule,
diff --git a/meilisearch-lib/src/index/error.rs b/meilisearch-lib/src/index/error.rs
index 5899b9356..92691cb14 100644
--- a/meilisearch-lib/src/index/error.rs
+++ b/meilisearch-lib/src/index/error.rs
@@ -11,14 +11,12 @@ pub type Result<T> = std::result::Result<T, IndexError>;
 pub enum IndexError {
     #[error("Internal error: {0}")]
     Internal(Box<dyn Error + Send + Sync + 'static>),
-    #[error("Document with id {0} not found.")]
+    #[error("Document `{0}` not found.")]
     DocumentNotFound(String),
     #[error("{0}")]
     Facet(#[from] FacetError),
     #[error("{0}")]
     Milli(#[from] milli::Error),
-    #[error("A primary key is already present. It's impossible to update it")]
-    ExistingPrimaryKey,
 }
 
 internal_error!(
@@ -35,21 +33,20 @@ impl ErrorCode for IndexError {
             IndexError::DocumentNotFound(_) => Code::DocumentNotFound,
             IndexError::Facet(e) => e.error_code(),
             IndexError::Milli(e) => MilliError(e).error_code(),
-            IndexError::ExistingPrimaryKey => Code::PrimaryKeyAlreadyPresent,
         }
     }
 }
 
 #[derive(Debug, thiserror::Error)]
 pub enum FacetError {
-    #[error("Invalid facet expression, expected {}, found: {1}", .0.join(", "))]
+    #[error("Invalid syntax for the filter parameter: `expected {}, found: {1}`.", .0.join(", "))]
     InvalidExpression(&'static [&'static str], Value),
 }
 
 impl ErrorCode for FacetError {
     fn error_code(&self) -> Code {
         match self {
-            FacetError::InvalidExpression(_, _) => Code::Facet,
+            FacetError::InvalidExpression(_, _) => Code::Filter,
         }
     }
 }
diff --git a/meilisearch-lib/src/index/updates.rs b/meilisearch-lib/src/index/updates.rs
index 772d27d76..1d19b7dd8 100644
--- a/meilisearch-lib/src/index/updates.rs
+++ b/meilisearch-lib/src/index/updates.rs
@@ -11,7 +11,7 @@ use uuid::Uuid;
 use crate::index_controller::updates::status::{Failed, Processed, Processing, UpdateResult};
 use crate::Update;
 
-use super::error::{IndexError, Result};
+use super::error::Result;
 use super::index::{Index, IndexMeta};
 
 fn serialize_with_wildcard<S>(
@@ -222,9 +222,6 @@ impl Index {
         match primary_key {
             Some(primary_key) => {
                 let mut txn = self.write_txn()?;
-                if self.primary_key(&txn)?.is_some() {
-                    return Err(IndexError::ExistingPrimaryKey);
-                }
                 let mut builder = UpdateBuilder::new(0).settings(&mut txn, self);
                 builder.set_primary_key(primary_key);
                 builder.execute(|_, _| ())?;
diff --git a/meilisearch-lib/src/index_controller/dump_actor/error.rs b/meilisearch-lib/src/index_controller/dump_actor/error.rs
index 9831f3931..49da8c90f 100644
--- a/meilisearch-lib/src/index_controller/dump_actor/error.rs
+++ b/meilisearch-lib/src/index_controller/dump_actor/error.rs
@@ -9,7 +9,7 @@ pub type Result<T> = std::result::Result<T, DumpActorError>;
 pub enum DumpActorError {
     #[error("Another dump is already in progress")]
     DumpAlreadyRunning,
-    #[error("Dump `{0}` not found")]
+    #[error("Dump `{0}` not found.")]
     DumpDoesNotExist(String),
     #[error("Internal error: {0}")]
     Internal(Box<dyn std::error::Error + Send + Sync + 'static>),
diff --git a/meilisearch-lib/src/index_controller/index_resolver/error.rs b/meilisearch-lib/src/index_controller/index_resolver/error.rs
index 661b9bde3..7e97b8ce5 100644
--- a/meilisearch-lib/src/index_controller/index_resolver/error.rs
+++ b/meilisearch-lib/src/index_controller/index_resolver/error.rs
@@ -3,6 +3,7 @@ use std::fmt;
 use meilisearch_error::{Code, ErrorCode};
 use tokio::sync::mpsc::error::SendError as MpscSendError;
 use tokio::sync::oneshot::error::RecvError as OneshotRecvError;
+use uuid::Uuid;
 
 use crate::{error::MilliError, index::error::IndexError};
 
@@ -12,17 +13,19 @@ pub type Result<T> = std::result::Result<T, IndexResolverError>;
 pub enum IndexResolverError {
     #[error("{0}")]
     IndexError(#[from] IndexError),
-    #[error("Index already exists")]
-    IndexAlreadyExists,
-    #[error("Index {0} not found")]
+    #[error("Index `{0}` already exists.")]
+    IndexAlreadyExists(String),
+    #[error("Index `{0}` not found.")]
     UnexistingIndex(String),
     #[error("A primary key is already present. It's impossible to update it")]
     ExistingPrimaryKey,
-    #[error("Internal Error: {0}")]
+    #[error("Internal Error: `{0}`")]
     Internal(Box<dyn std::error::Error + Send + Sync + 'static>),
+    #[error("Internal Error: Index uuid `{0}` is already assigned.")]
+    UUIdAlreadyExists(Uuid),
     #[error("{0}")]
     Milli(#[from] milli::Error),
-    #[error("Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_).")]
+    #[error("`{0}` is not a valid index uid. Index uid can be an integer or a string containing only alphanumeric characters, hyphens (-) and underscores (_).")]
     BadlyFormatted(String),
 }
 
@@ -53,10 +56,11 @@ impl ErrorCode for IndexResolverError {
     fn error_code(&self) -> Code {
         match self {
             IndexResolverError::IndexError(e) => e.error_code(),
-            IndexResolverError::IndexAlreadyExists => Code::IndexAlreadyExists,
+            IndexResolverError::IndexAlreadyExists(_) => Code::IndexAlreadyExists,
             IndexResolverError::UnexistingIndex(_) => Code::IndexNotFound,
             IndexResolverError::ExistingPrimaryKey => Code::PrimaryKeyAlreadyPresent,
             IndexResolverError::Internal(_) => Code::Internal,
+            IndexResolverError::UUIdAlreadyExists(_) => Code::Internal,
             IndexResolverError::Milli(e) => MilliError(e).error_code(),
             IndexResolverError::BadlyFormatted(_) => Code::InvalidIndexUid,
         }
diff --git a/meilisearch-lib/src/index_controller/index_resolver/index_store.rs b/meilisearch-lib/src/index_controller/index_resolver/index_store.rs
index dcc024121..302b23c2f 100644
--- a/meilisearch-lib/src/index_controller/index_resolver/index_store.rs
+++ b/meilisearch-lib/src/index_controller/index_resolver/index_store.rs
@@ -64,7 +64,7 @@ impl IndexStore for MapIndexStore {
         }
         let path = self.path.join(format!("{}", uuid));
         if path.exists() {
-            return Err(IndexResolverError::IndexAlreadyExists);
+            return Err(IndexResolverError::UUIdAlreadyExists(uuid));
         }
 
         let index_size = self.index_size;
diff --git a/meilisearch-lib/src/index_controller/index_resolver/uuid_store.rs b/meilisearch-lib/src/index_controller/index_resolver/uuid_store.rs
index f10bad757..94c3ddbb5 100644
--- a/meilisearch-lib/src/index_controller/index_resolver/uuid_store.rs
+++ b/meilisearch-lib/src/index_controller/index_resolver/uuid_store.rs
@@ -100,7 +100,7 @@ impl HeedUuidStore {
         let mut txn = env.write_txn()?;
 
         if db.get(&txn, &name)?.is_some() {
-            return Err(IndexResolverError::IndexAlreadyExists);
+            return Err(IndexResolverError::IndexAlreadyExists(name));
         }
 
         db.put(&mut txn, &name, uuid.as_bytes())?;
diff --git a/meilisearch-lib/src/index_controller/snapshot.rs b/meilisearch-lib/src/index_controller/snapshot.rs
index c0d409990..07bf75199 100644
--- a/meilisearch-lib/src/index_controller/snapshot.rs
+++ b/meilisearch-lib/src/index_controller/snapshot.rs
@@ -222,10 +222,11 @@ mod test {
         setup();
 
         let mut uuid_store = MockUuidStore::new();
-        uuid_store
-            .expect_snapshot()
-            .once()
-            .returning(move |_| Box::pin(err(IndexResolverError::IndexAlreadyExists)));
+        uuid_store.expect_snapshot().once().returning(move |_| {
+            Box::pin(err(IndexResolverError::IndexAlreadyExists(
+                "test".to_string(),
+            )))
+        });
 
         let mut index_store = MockIndexStore::new();
         index_store.expect_get().never();
@@ -264,9 +265,9 @@ mod test {
         let mut indexes = uuids.clone().into_iter().map(|uuid| {
             let mocker = Mocker::default();
             // index returns random error
-            mocker
-                .when("snapshot")
-                .then(|_: &Path| -> IndexResult<()> { Err(IndexError::ExistingPrimaryKey) });
+            mocker.when("snapshot").then(|_: &Path| -> IndexResult<()> {
+                Err(IndexError::DocumentNotFound("1".to_string()))
+            });
             mocker.when("uuid").then(move |_: ()| uuid);
             Index::faux(mocker)
         });
diff --git a/meilisearch-lib/src/index_controller/updates/error.rs b/meilisearch-lib/src/index_controller/updates/error.rs
index 39a73c7c4..27260079e 100644
--- a/meilisearch-lib/src/index_controller/updates/error.rs
+++ b/meilisearch-lib/src/index_controller/updates/error.rs
@@ -14,7 +14,7 @@ pub type Result<T> = std::result::Result<T, UpdateLoopError>;
 #[derive(Debug, thiserror::Error)]
 #[allow(clippy::large_enum_variant)]
 pub enum UpdateLoopError {
-    #[error("Update {0} not found.")]
+    #[error("Task `{0}` not found.")]
     UnexistingUpdate(u64),
     #[error("Internal error: {0}")]
     Internal(Box<dyn Error + Send + Sync + 'static>),
@@ -24,9 +24,8 @@ pub enum UpdateLoopError {
     FatalUpdateStoreError,
     #[error("{0}")]
     DocumentFormatError(#[from] DocumentFormatError),
-    // TODO: The reference to actix has to go.
-    #[error("{0}")]
-    PayloadError(#[from] actix_web::error::PayloadError),
+    #[error("The provided payload reached the size limit.")]
+    PayloadTooLarge,
     #[error("A {0} payload is missing.")]
     MissingPayload(DocumentAdditionFormat),
     #[error("{0}")]
@@ -48,6 +47,15 @@ impl From<tokio::sync::oneshot::error::RecvError> for UpdateLoopError {
     }
 }
 
+impl From<actix_web::error::PayloadError> for UpdateLoopError {
+    fn from(other: actix_web::error::PayloadError) -> Self {
+        match other {
+            actix_web::error::PayloadError::Overflow => Self::PayloadTooLarge,
+            _ => Self::Internal(Box::new(other)),
+        }
+    }
+}
+
 internal_error!(
     UpdateLoopError: heed::Error,
     std::io::Error,
@@ -59,14 +67,11 @@ internal_error!(
 impl ErrorCode for UpdateLoopError {
     fn error_code(&self) -> Code {
         match self {
-            Self::UnexistingUpdate(_) => Code::NotFound,
+            Self::UnexistingUpdate(_) => Code::TaskNotFound,
             Self::Internal(_) => Code::Internal,
             Self::FatalUpdateStoreError => Code::Internal,
             Self::DocumentFormatError(error) => error.error_code(),
-            Self::PayloadError(error) => match error {
-                actix_web::error::PayloadError::Overflow => Code::PayloadTooLarge,
-                _ => Code::Internal,
-            },
+            Self::PayloadTooLarge => Code::PayloadTooLarge,
             Self::MissingPayload(_) => Code::MissingPayload,
             Self::IndexError(e) => e.error_code(),
         }
diff --git a/meilisearch-lib/src/index_controller/updates/mod.rs b/meilisearch-lib/src/index_controller/updates/mod.rs
index 07ceed92b..3f2a2ef32 100644
--- a/meilisearch-lib/src/index_controller/updates/mod.rs
+++ b/meilisearch-lib/src/index_controller/updates/mod.rs
@@ -174,15 +174,18 @@ impl UpdateLoop {
                     }
 
                     let reader = Cursor::new(buffer);
-                    match format {
+                    let document_count = match format {
                         DocumentAdditionFormat::Json => read_json(reader, &mut *update_file)?,
                         DocumentAdditionFormat::Csv => read_csv(reader, &mut *update_file)?,
                         DocumentAdditionFormat::Ndjson => read_ndjson(reader, &mut *update_file)?,
+                    };
+
+                    if document_count > 0 {
+                        update_file.persist()?;
+                        Ok(())
+                    } else {
+                        Err(UpdateLoopError::MissingPayload(format))
                     }
-
-                    update_file.persist()?;
-
-                    Ok(())
                 })
                 .await??;
 
diff --git a/meilisearch-lib/src/index_controller/updates/store/mod.rs b/meilisearch-lib/src/index_controller/updates/store/mod.rs
index 81525c3fd..336d648a0 100644
--- a/meilisearch-lib/src/index_controller/updates/store/mod.rs
+++ b/meilisearch-lib/src/index_controller/updates/store/mod.rs
@@ -731,7 +731,7 @@ mod test {
                 mocker
                     .when::<Processing, std::result::Result<Processed, Failed>>("handle_update")
                     .once()
-                    .then(|update| Err(update.fail(IndexError::ExistingPrimaryKey)));
+                    .then(|update| Err(update.fail(IndexError::DocumentNotFound("1".to_string()))));
 
                 Box::pin(ok(Some(Index::faux(mocker))))
             });