diff --git a/openapi.yaml b/openapi.yaml
index 2cf5f37..3aba7df 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -10165,7 +10165,11 @@ components:
           example: en
         prompt:
           type: string
-          description: Optional text to bias decoding.
+          description: >-
+            Optional text to bias decoding. Supported only on Whisper-family
+            models (e.g. `openai/whisper-large-v3`). Other STT models
+            (e.g. `nvidia/parakeet-tdt-0.6b-v3`) accept the field for API
+            compatibility but ignore it.
         response_format:
           type: string
           description: The format of the response
@@ -10400,7 +10404,11 @@ components:
           example: en
         prompt:
           type: string
-          description: Optional text to bias decoding.
+          description: >-
+            Optional text to bias decoding. Supported only on Whisper-family
+            models (e.g. `openai/whisper-large-v3`). Other STT models
+            (e.g. `nvidia/parakeet-tdt-0.6b-v3`) accept the field for API
+            compatibility but ignore it.
         response_format:
           type: string
           description: The format of the response