Python: use field description over pydantic constraint objects in schema builder - #14444
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…riptions build_model_schema() preferred FieldInfo.metadata over FieldInfo.description when deriving field descriptions. In pydantic v2, FieldInfo.metadata is a list of constraint objects (annotated_types.Ge, Gt, ...), so for any field declared with a constraint (e.g. Field(description=..., ge=0)) the real description was replaced by the constraint object. The resulting schema carried a non-string 'description' and json.dumps() of the function-calling tool payload failed with 'TypeError: Object of type Ge is not JSON serializable'. Only treat str and dict-with-'description' entries in metadata as descriptions (these come from Annotated metadata), and fall back to FieldInfo.description otherwise.
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Fixes #14443.
The field-description extraction now only accepts
strmetadata entries (or dicts carrying a description) and falls back tofield_info.description, instead of blindly takingFieldInfo.metadata[0], which under pydantic v2 is a constraint object likeGe(ge=0). Constrained fields keep their real description and the generated schema serializes cleanly.2 regression tests (constrained field keeps description; schema JSON-serializable) fail on main and pass here;
tests/unit/schemagreen, connectors/mcp unaffected (23 passed).