Unverified50% confidenceFactExact time
Different models adhere to JSON Schema to varying degrees and may omit required fields, write numbers as strings, change key names in nested objects, or return explanatory text instead of JSON.
1
Sources
50%
Confidence
Long-term
Relevance
10/17/2026
First Seen
Sources
Related Entities
Related Claims
UnverifiedJSON Schema can only express structural and simple value constraints such as types, enums, regex patterns, date formats, numeric upper and lower bounds, required fields, and array lengths; it cannot express arbitrary custom functions, cross-field comparisons, or transformations that change the shape of the data.79% similarUnverifiedProviders do not send the user's JSON to the model as-is; instead they rewrite it into an internal format and add their own instructions, so the real token numbers will differ and vary by provider; it is recommended to verify by comparing the difference between with-tools and without-tools via the usage.prompt_tokens field.79% similarUnverifiedEven when using structured output interfaces, occasional format drift or missing fields from the model still occur, and production environments typically require adding JSON validation and exception fallback mechanisms.78% similarUnverifiedJSON Schema annotation keywords such as title, description, and examples do not affect validation logic, but large models rely on these annotations to understand parameter meanings78% similarUnverified在FastMCP中，函数的类型提示和文档字符串会自动转换为符合JSON Schema规范的工具模式，无需手写JSON Schema78% similar
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