Mistral OCR: inline base64 fails with 'Failed to fetch document'

Mistral OCR: inline base64 fails with 'Failed to fetch document'

TL;DR

Do not inline base64 into the document field when calling Mistral OCR. Upload the file first with purpose=ocr, fetch a signed URL with an expiry, and send that URL as document_url. If you get 'Failed to fetch document', check that the URL is reachable by Mistral's servers, not just by you.

Use this when you run into the situation in the title.

When not to use this skill: unrelated tasks. It covers only the procedure above.

Compatibility

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Details

Context: GitHub issue (mistralai/platform-docs-public #269): sending an inline base64 data URI as imageurl to POST /v1/ocr returns 400 with 'Failed to fetch document'. The reporter followed the docs example and still hit it, so it is not just a formatting slip. Gotcha that trips agents: Mistral OCR wants a URL it can fetch. For local files, use the three-step flow instead: upload to POST /files with purpose=ocr, grab a signed URL from GET /files/[id]/url, and pass that as documenturl.

Source: GitHub issue (mistralai/platform-docs-public #269): sending an inline base64 data URI as imageurl to POST /v1/ocr returns 400 with 'Failed to fetch document'. The reporter followed the docs example and still hit it, so it is not just a formatting slip. Gotcha that trips agents: Mistral OCR wants a URL it can fetch. For local files, use the three-step flow instead: upload to POST /files with purpose=ocr, grab a signed URL from GET /files/[id]/url, and pass that as documenturl.

Verified resolution: Do not inline base64 into the document field when calling Mistral OCR. Upload the file first with purpose=ocr, fetch a signed URL with an expiry, and send that URL as document_url. If you get 'Failed to fetch document', check that the URL is reachable by Mistral's servers, not just by you.

Source URL: https://github.com/mistralai/platform-docs-public/issues/269