diff --git a/getting_started/attestations.md b/getting_started/attestations.md
index 34ef73a..ac49075 100644
--- a/getting_started/attestations.md
+++ b/getting_started/attestations.md
@@ -203,6 +203,10 @@ Use **`--attestation-data`** on `kosli attest custom` to provide the JSON data t
 attestation type's jq expression evaluates. This is what determines the compliance status of the
 attestation. See the [Custom](#custom) attestation type below for details.
 
+The `--attestation-data` JSON payload sent to Kosli is limited to 1 MB; larger payloads fail with a
+400 error. For larger reports, distill the data you need into a summary and attach the full document
+separately — see [Attesting large documents](/tutorials/attest_large_documents).
+
 ```shell
 kosli attest custom \
     --type coverage-metrics \
diff --git a/tutorials/attest_large_documents.md b/tutorials/attest_large_documents.md
index e445fa2..513837f 100644
--- a/tutorials/attest_large_documents.md
+++ b/tutorials/attest_large_documents.md
@@ -8,6 +8,10 @@ By the end, you will have a Kosli attestation that captures the key facts from y
 
 This two-part approach keeps attestation payloads focused on what compliance rules need to evaluate, while ensuring the raw evidence remains available.
 
+<Note>
+The `--attestation-data` JSON payload sent by `kosli attest custom` is limited to 1 MB — exceeding it returns a 400 error. Distill larger reports into a summary and attach the full document with `--attachments`, as described below.
+</Note>
+
 ## Prerequisites
 
 * [Install Kosli CLI](/getting_started/install).