{"record":{"id":"6c4af7b6279967dc","repo":"googleapis/mcp-toolbox","slug":"invalid-params-6c4af7","errorCode":"INVALID_PARAMS","errorMessage":"_meta error: missing io.modelcontextprotocol/protocolVersion","messagePattern":"_meta error: missing io\\.modelcontextprotocol/protocolVersion","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"internal/server/mcp/v20260728/method.go","lineNumber":68,"sourceCode":"\t\treturn toolsCallHandler(ctx, id, g, primitiveMgr, body, header)\n\tcase PROMPTS_LIST:\n\t\treturn promptsListHandler(ctx, id, primitiveMgr, g, body, header)\n\tcase PROMPTS_GET:\n\t\treturn promptsGetHandler(ctx, id, g, primitiveMgr, body, header)\n\tdefault:\n\t\terr := fmt.Errorf(\"invalid method %s\", method)\n\t\treturn jsonrpc.NewError(id, jsonrpc.METHOD_NOT_FOUND, err.Error(), nil), err\n\t}\n}\n\n// validateMetadata checks the metadata of every requests\nfunc validateMetadata(id jsonrpc.RequestId, params RequestParams, stdio bool) (any, error) {\n\t// Check _meta field for protocol version\n\tif params.Meta != nil {\n\t\t// check for protocol version metadata\n\t\tv := params.Meta.ProtocolVersion\n\t\tif v == \"\" {\n\t\t\tmetaErr := fmt.Errorf(\"_meta error: missing io.modelcontextprotocol/protocolVersion\")\n\t\t\treturn jsonrpc.NewError(id, jsonrpc.INVALID_PARAMS, metaErr.Error(), nil), metaErr\n\t\t}\n\t\t// do not have to verify header for stdio; already verified during stdio\n\t\t// message processing\n\t\tif !stdio {\n\t\t\tif PROTOCOL_VERSION != v {\n\t\t\t\tmetaErr := fmt.Errorf(\"_meta error: header mismatch: MCP-Protocol-Version header value '%s' does not match body value '%s'\", PROTOCOL_VERSION, v)\n\t\t\t\treturn jsonrpc.NewHeaderMismatchedError(id, metaErr), metaErr\n\t\t\t}\n\t\t}\n\n\t\t// check for clientInfo\n\t\tclientInfo := params.Meta.ClientInfo\n\t\tif clientInfo.Version == \"\" || clientInfo.Name == \"\" {\n\t\t\tmetaErr := fmt.Errorf(\"_meta error: missing field from io.modelcontextprotocol/clientInfo\")\n\t\t\treturn jsonrpc.NewError(id, jsonrpc.INVALID_PARAMS, metaErr.Error(), nil), metaErr\n\t\t}\n\t\t// check for clientCapabilities","sourceCodeStart":50,"sourceCodeEnd":86,"githubUrl":"https://github.com/googleapis/mcp-toolbox/blob/8cc6e09de2ad7b8bffc77751799585a1401a48eb/internal/server/mcp/v20260728/method.go#L50-L86","documentation":"Error \"_meta error: missing io.modelcontextprotocol/protocolVersion\" thrown in googleapis/mcp-toolbox.","triggerScenarios":"Thrown at internal/server/mcp/v20260728/method.go:68 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"8cc6e09de2ad7b8bffc77751799585a1401a48eb","analyzedAt":"2026-09-05T01:10:36.887Z","contentChangedAt":"2026-09-05T01:10:36.887Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}