fix(vertex): project tool schemas onto the subset Google accepts - #181
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Google's `Schema` parser is strict and rejects the *entire request* over a
single unknown JSON-Schema keyword anywhere in a tool declaration:
400 Invalid JSON payload received. Unknown name "exclusiveMinimum" at
'tools[0].function_declarations[4].parameters.properties[0].value'
Tool schemas written against full JSON Schema — which Anthropic and OpenAI
accept verbatim — therefore made every Gemini request fail. `exclusiveMinimum`,
`additionalProperties` and `oneOf` are the ones that show up in practice.
`sanitize_google_schema` projects a schema onto the documented keyword set,
recursing through `properties`, `items` and `anyOf`. Dropping a constraint is
deliberate and lossy: the tool's description carries the intent for the model
and the caller validates arguments anyway — losing a bound is survivable,
losing every request to a 400 is not.
Exported, because Gemini Live's BidiGenerateContent WebSocket API uses the
same `Schema` type and needs the identical projection.
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Problem
Google's
Schemaparser is strict and rejects the entire request over a single unknown JSON-Schema keyword anywhere in a tool declaration:Tool schemas written against full JSON Schema — which Anthropic and OpenAI accept verbatim — therefore made every Gemini request fail. The keywords that show up in practice:
exclusiveMinimum,additionalProperties,oneOf.Fix
sanitize_google_schemaprojects a schema onto the documented keyword set, recursing throughproperties,itemsandanyOf.vertex.rsapplies it when buildingfunction_declarations.Dropping a constraint is deliberate and lossy: the tool's description carries the intent for the model and the caller validates arguments anyway. Losing a bound is survivable; losing every request to a 400 is not.
The function is exported because Gemini Live's
BidiGenerateContentWebSocket API uses the sameSchematype and needs the identical projection — the Tutor app's realtime path consumes it from here rather than keeping a second copy.Verification
Reproduced and verified against the live API with a real 20-tool set:
400 INVALID_ARGUMENT, three field violations (exclusiveMinimum×2,additionalProperties)cargo test -p llmgreen (3 new tests), clippy clean,cargo fmtapplied.