GraphQL MCP Server

#!/usr/bin/env node import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"; import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"; import { parse } from "graphql/language"; import { z } from "zod"; import { introspectEndpoint } from "./helpers/introspection.js"; const EnvSchema = z.object({ ENDPOINT: z.string().url().default("http://localhost:4000/graphql"), ALLOW_MUTATIONS: z .enum(["true", "false"]) .transform((value) => value === "true") .default("false"), HEADERS: z .string() .default("{}") .transform((val) => { try { return JSON.parse(val); } catch (e) { throw new Error("HEADERS must be a valid JSON string"); } }), }); const env = EnvSchema.parse(process.env); const server = new McpServer({ name: "GQL-mcp-server", version: "1.0.0", description: `GraphQL MCP server for ${env.ENDPOINT}`, }); server.resource( "schema", new URL(env.ENDPOINT).href, async (uri: any) => { try { let schema = await introspectEndpoint(env.ENDPOINT, env.HEADERS); return { contents: [ { uri: uri.href, text: schema, }, ], }; } catch (error) { throw new Error(`Failed to get GraphQL schema: ${error}`); } } ); server.tool( "inspect", "Inspect this server", { __ignore__: z .boolean() .default(false) .describe("This does not do anything"), }, async () => { console.log("Inspecting server"); return { content: [ { type: "text", text: "This is a test", }, ], }; } ); server.tool( "introspect", "Introspect the GraphQL schema, use this tool before doing a query to get the schema information if you do not have it available as a resource already.", { // This is a workaround to help clients that can't handle an empty object as an argument // They will often send undefined instead of an empty object which is not allowed by the schema __ignore__: z .boolean() .default(false) .describe("This does not do anything"), }, async () => { try { const schema = await introspectEndpoint(env.ENDPOINT, env.HEADERS); return { content: [ { type: "text", text: schema, }, ], }; } catch (error) { return { isError: true, content: [ { type: "text", text: `Failed to introspect schema: ${error}`, }, ], }; } } ); server.tool( "query", "Query a GraphQL endpoint with the given query and variables", { query: z.string(), variables: z.string().optional(), }, async ({ query, variables }) => { try { const parsedQuery = parse(query); // Check if the query is a mutation const isMutation = parsedQuery.definitions.some( (def) => def.kind === "OperationDefinition" && def.operation === "mutation" ); if (isMutation && !env.ALLOW_MUTATIONS) { return { isError: true, content: [ { type: "text", text: "Mutations are not allowed unless you enable them in the configuration. Please use a query operation instead.", }, ], }; } } catch (error) { return { isError: true, content: [ { type: "text", text: `Invalid GraphQL query: ${error}`, }, ], }; } try { const response = await fetch(env.ENDPOINT, { method: "POST", headers: { "Content-Type": "application/json", ...env.HEADERS, }, body: JSON.stringify({ query, variables, }), }); if (!response.ok) { const responseText = await response.text(); return { isError: true, content: [ { type: "text", text: `GraphQL request failed: ${response.statusText}\n${responseText}`, }, ], }; } const data = (await response.json()) as any; if (data.errors && data.errors.length > 0) { // Contains GraphQL errors return { isError: true, content: [ { type: "text", text: `The GraphQL response has errors, please fix the query: ${JSON.stringify( data, null, 2 )}`, }, ], }; } return { content: [ { type: "text", text: JSON.stringify(data, null, 2), }, ], }; } catch (error) { throw new Error(`Failed to execute GraphQL query: ${error}`); } } ); async function main() { const transport = new StdioServerTransport(); await server.connect(transport); console.error( `Started graphql mcp server for endpoint: ${env.ENDPOINT}` ); } main().catch((error) => { console.error(`Fatal error in main(): ${error}`); process.exit(1); });