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fix(mcp): send empty properties for tools without arguments - #82
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An MCP tool that takes no arguments has no "properties" in its input schema, so the unmarshal leaves the property map nil. Before mudler#81 the tool was sent as a jsonschema.Definition, whose MarshalJSON encodes a nil map as {}. mcpToolParameters has no such hook, so the tool went out with "properties": null. vLLM validates every tool schema and rejects the whole request with a 400 ("None is not of type 'object'"), so one argument-less MCP tool broke every call to such a server. Strict mode was not affected: it already fills in an empty properties object. Tool() now sends an empty object when the map is nil. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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An MCP tool that takes no arguments has no
propertiesin its input schema, so the unmarshal leaves the property map nil. Before #81 the tool was sent as ajsonschema.Definition, whoseMarshalJSONencodes a nil map as{}.mcpToolParametershas no such hook, so the tool went out as:{"type":"object","properties":null}vLLM validates every tool schema and rejects the whole request with a 400, so one argument-less MCP tool breaks every call:
Strict mode was not affected, because it already fills in an empty
propertiesobject.Tool()now sends an empty object when the map is nil.mcp_params_test.gocovers it: it fails on main with{"type":"object","properties":null}and passes with the fix.Testing:
go test . -ginkgo.label-filter='!e2e'andgo vet .pass.🤖 Generated with Claude Code