fix: strip unsupported JSON Schema fields for Google GenAI provider#1466
fix: strip unsupported JSON Schema fields for Google GenAI provider#1466Br1an67 wants to merge 1 commit intoMoonshotAI:mainfrom
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| unsupported_keys = {"$schema", "$id", "$ref", "$comment", "definitions", "$defs"} | ||
| parameters = {k: v for k, v in parameters.items() if k not in unsupported_keys} |
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Filtering out top-level definitions/$defs here can invalidate otherwise valid tool schemas, because nested properties may still contain $ref pointers to those removed definitions (a common shape for nested Pydantic/JSON-Schema models). In that case the provider receives a dangling-reference schema and tool declarations can be rejected or lose parameter structure, so tool calling still breaks for nested parameter types.
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When MCP tools provide standard JSON Schema parameters containing metadata fields like $schema, the google-genai SDK's Pydantic model rejects them with extra_forbidden validation errors. Use the existing deref_json_schema() utility to properly resolve $ref entries and remove $defs/definitions, preserving nested parameter types. Then strip remaining metadata fields ($schema, $id, $comment) that the SDK doesn't support. Fixes MoonshotAI#734
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| # nested parameter types are preserved instead of becoming dangling refs | ||
| from kosong.utils.jsonschema import deref_json_schema | ||
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| parameters = deref_json_schema(parameters) |
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$ref schemas
Calling deref_json_schema() unconditionally here can crash tool conversion for valid self-referential schemas (for example MCP tools that model tree/graph inputs), because the resolver recursively inlines local $ref targets without cycle detection and will recurse forever on references like "$ref": "#"/mutual refs. In that case tool_to_google_genai() now raises before the request is sent, whereas this path previously passed the schema through, so Google provider tool calls regress from "SDK may reject" to a hard local failure.
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| unsupported_keys = {"$schema", "$id", "$comment"} | ||
| parameters = {k: v for k, v in parameters.items() if k not in unsupported_keys} |
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🟡 Unsupported JSON Schema keys only stripped at top level, not recursively
The stripping of keys rejected by the Google GenAI SDK ($schema, $id, $comment) is applied only to the top-level of parameters via a shallow dict comprehension at line 367. If any nested schema object (e.g., inside properties, items, allOf, etc.) contains these keys, they will remain and still trigger the extra_forbidden validation error from the SDK's Pydantic model — the same error this code intends to fix.
Example: nested $comment survives stripping
A tool with parameters like:
{"type": "object", "$comment": "top-level", "properties": {"x": {"type": "string", "$comment": "nested"}}}After line 367, the top-level $comment is removed, but properties.x.$comment remains, causing the same SDK validation error.
While $schema is conventionally top-level only, $comment is valid at any nesting depth per the JSON Schema spec, and tool parameter schemas from MCP tools or other non-Pydantic sources could include it at nested levels.
Prompt for agents
In packages/kosong/src/kosong/contrib/chat_provider/google_genai.py, the tool_to_google_genai function (around lines 353-376) strips unsupported keys ($schema, $id, $comment) only at the top level of the parameters dict (line 367). This should be done recursively to also strip these keys from nested schema objects. Consider adding a helper function like:
def _strip_unsupported_keys(schema: dict) -> dict:
unsupported_keys = {"$schema", "$id", "$comment"}
result = {k: v for k, v in schema.items() if k not in unsupported_keys}
for key, value in result.items():
if isinstance(value, dict):
result[key] = _strip_unsupported_keys(value)
elif isinstance(value, list):
result[key] = [
_strip_unsupported_keys(item) if isinstance(item, dict) else item
for item in value
]
return result
Then replace lines 366-367 with: parameters = _strip_unsupported_keys(parameters)
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|
Closing this PR — the issue was independently fixed on main via commit 45333f0 which uses |
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Problem
When MCP tools provide standard JSON Schema parameters containing metadata fields like
$schema, the google-genai SDK's Pydantic model rejects them withextra_forbiddenvalidation errors, preventing tool calls.Fix
Strip unsupported JSON Schema metadata fields (
$schema,$id,$ref,$comment,definitions,$defs) from tool parameters intool_to_google_genai()before passing to the SDK.Fixes #734