How to Get Clean JSON Output from DeepSeek API Without Markdown Fences?

Question

1

Using DeepSeek's API for a small tool. I ask for JSON and it keeps wrapping the output in ```json fences or adding "Here is your JSON:" before it. My parser dies every time. How do I make it behave?

1 Answer

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Answer 1

Three things, do all of them.

Turn on JSON mode in the API call if it's available for the model you're using. That forces valid JSON.
In your system prompt, be blunt: "Output only a raw JSON object. No explanation. No markdown. No code fences." And give it an example of the exact shape you want, that helps more than any instruction.
And then, this is the part everyone skips, assume it'll still mess up sometimes. Before parsing, strip anything that looks like ``` from the start and end. Wrap the parse in try/except. If it fails, send the bad output back with "fix this so it's valid JSON" or just retry. No model gets formatting right 100% of the time, so build for that instead of hoping.