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HTTP 415 Unsupported Media Type

The request body format is not supported — usually a missing or wrong Content-Type header.

4xx · Client error✗ not retryable — fix the request instead

In AI APIs specifically

Sending JSON without Content-Type: application/json, or uploading files with the wrong multipart encoding.

Fix checklist

  • Set Content-Type: application/json on JSON requests.
  • Use multipart/form-data for file uploads exactly as documented.

Spec: RFC reference