mcp4gql

import { z } from "zod"; import { executeGraphQL } from "../graphqlClient"; import { McpError, ErrorCode } from "@modelcontextprotocol/sdk/types.js"; // Define the Zod schema for the input parameters export const ExecutorSchemaInput = z.object({ query: z.string().describe("The GraphQL query string to execute."), variables: z .record(z.unknown()) .optional() .describe("An optional object containing variables for the query."), operationName: z .string() .optional() .describe( "An optional name for the operation, if the query contains multiple operations." ), }); // Define the Zod schema for the output (general GraphQL response structure) // We expect the result of executeGraphQL which includes data and errors export const ExecutorSchemaOutput = z.object({ data: z .record(z.unknown()) .nullable() .optional() .describe("The data returned by the GraphQL server."), errors: z .array(z.object({ message: z.string() /* ... other optional fields */ })) .optional() .describe("Any errors encountered during query execution."), }); /** * Handler function for the executeGraphQLQuery tool. * Executes a given GraphQL query against the configured endpoint. * * @param input The validated input parameters matching ExecutorSchemaInput. * @returns The result of the GraphQL query execution. * @throws {McpError} If the query execution fails. */ export async function handleExecution( input: z.infer<typeof ExecutorSchemaInput> ): Promise<z.infer<typeof ExecutorSchemaOutput>> { const { query, variables, operationName } = input; try { console.error(`Executing GraphQL query: ${operationName || "unnamed"}...`); const response = await executeGraphQL<z.infer<typeof ExecutorSchemaOutput>>( query, variables, operationName ); // GraphQL endpoints often return 200 OK even if there are query errors. // These are included in the 'errors' array in the response body. if (response.errors && response.errors.length > 0) { const errorMessages = response.errors.map((e) => e.message).join("; "); console.error( `GraphQL query ${ operationName || "unnamed" } returned errors: ${errorMessages}`, response.errors ); // We return the full response including data and errors as per the MCP flow // The client consuming the MCP tool will decide how to handle the errors field. // No McpError is thrown here unless the request itself failed (handled in executeGraphQL) } console.error(`GraphQL query ${operationName || "unnamed"} executed.`); return response; // Return the full response { data?: ..., errors?: ... } } catch (error) { // This catches errors thrown by executeGraphQL (network, HTTP errors, etc.) console.error( `Error executing GraphQL query ${operationName || "unnamed"}:`, error ); if (error instanceof McpError) { // Re-throw McpErrors directly throw error; } // Wrap unexpected errors throw new McpError( ErrorCode.InternalError, `An unexpected error occurred while executing the GraphQL query '${ operationName || "unnamed" }'.`, { cause: error as Error } ); } }