Graphql Bridge MCP Server

mcp-graphql-bridge

A generic MCP (Model Context Protocol) server that bridges any GraphQL API to Claude Code. It introspects your GraphQL schema and exposes each query and mutation as an individual tool, letting Claude interact with your API directly.

How it works

On startup the server will:

1. Look for a schema-introspection.json file in the working directory (fast, no network call)
2. If not found, run live introspection against GRAPHQL_INTROSPECTION_URL
3. Register one tool per query (query__<name>) and one per mutation (mutation__<name>)
4. Always register a generic execute_graphql fallback tool and a get_type_details explorer tool

Requirements

• Node.js >= 20

Setup

Step 1: Install

Option A: Install from npm (recommended)

npm install -g mcp-graphql-bridge

Option B: Clone and build from source

git clone https://github.com/murilojrpereira/mcp-graphql-bridge.git
cd mcp-graphql-bridge
npm install
npm run build

Step 2: Configure environment variables

For schemas with hundreds of fields (GitHub's GraphQL API has 284 root fields — 32 queries, 252 mutations), GRAPHQL_MAX_TOOLS and GRAPHQL_INCLUDE_MUTATIONS are what keep registration bounded and predictable. If the cap truncates the schema, stderr logs exactly how many queries/mutations were registered vs. available.

No configuration is required to try the server — with nothing set, it starts against the public demo API above and logs that it's doing so. See docs/architecture.md for the full token model and why the GraphQL endpoint is fixed per deployment rather than a per-request parameter.

You can set these in a .env file at the project root:

GRAPHQL_API_URL=https://your-api.example.com/graphql
GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql
GRAPHQL_TOKEN=your-bearer-token

Or pass them directly via the claude mcp add command (see below).

Step 3: (Optional) Pre-generate schema snapshot

By default the server introspects your schema live on startup — no file needed, and it automatically retries at a shallower query depth if your API rejects the full-depth attempt (some APIs, especially CDN-fronted ones, enforce a query depth limit). Use this step only if your API has introspection disabled entirely in production, or you want faster startup times:

curl -s -X POST https://your-api.example.com/graphql \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer your-bearer-token" \
  -d '{"query":"{ __schema { queryType { fields { name description args { name description defaultValue type { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name } } } } } } } } type { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name } } } } } } } } } mutationType { fields { name description args { name description defaultValue type { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name } } } } } } } } type { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name ofType { kind name } } } } } } } } } } }"}' \
  > schema-introspection.json

If your API rejects this with a depth/complexity-limit error, shrink the ofType { ... } nesting (each level resolves one more NonNull/List wrapper — most real-world types need 2-3 levels; only doubly-wrapped lists like [[Int!]!]! need more).

Adding to Claude Code

Option A: User scope (just for you)

If installed from npm:

claude mcp add --transport stdio \
  --env GRAPHQL_API_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_TOKEN=your-bearer-token \
  graphql-bridge -- mcp-graphql-bridge

If cloned from source:

claude mcp add --transport stdio \
  --env GRAPHQL_API_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_TOKEN=your-bearer-token \
  graphql-bridge -- node /absolute/path/to/mcp-graphql-bridge/dist/index.js

Important: Make sure to use mcp-graphql-bridge/dist/index.js (the compiled output), not mcp-graphql-bridge/index.js. The TypeScript source must be built first with npm run build, and the entry point is in the dist/ folder.

Option B: Project scope (shared with your team via .mcp.json)

claude mcp add --transport stdio --scope project \
  --env GRAPHQL_API_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_TOKEN=your-bearer-token \
  graphql-bridge -- mcp-graphql-bridge

Note: Use absolute paths. All --env and --transport flags must come before the server name.

Verify the connection

claude mcp list

Then in a Claude Code session, run /mcp to see available servers and tools.

Examples

Two worked walkthroughs — a small public schema with no configuration needed, then a large, real enterprise-scale schema requiring auth and tool-count limits.

Example 1: Countries API (small schema, no auth)

This is the zero-config default — nothing to install or configure beyond the server itself.

1. Add the server with no environment variables at all:

   claude mcp add --transport stdio graphql-countries -- mcp-graphql-bridge
   

2. Restart Claude Code (or run /mcp to confirm graphql-countries is connected). You should see tools like query__country, query__countries, and query__continents.

3. Ask Claude:

   Using graphql-countries, find the country with code "BR", then list its continent's other countries.

   Claude calls query__country({ code: "BR", __fields: "{ name continent { code name } }" }), then query__continent or query__countries({ __fields: "{ name }" }) filtered by the result.

4. Try an invalid code to see error passthrough:

   Look up the country with code "ZZZ".

   Returns the GraphQL API's own error text — the bridge passes it through rather than masking it.

Example 2: GitHub GraphQL API (large schema, auth + tool limits)

GitHub's GraphQL API has 284 root fields (32 queries, 252 mutations) — far more than the GRAPHQL_MAX_TOOLS default of 128, and it needs a token for every request, including introspection (unlike GitHub's REST API, which allows some anonymous reads).

1. Add the server, scoped to read-only access:

   export GH_TOKEN=ghp_your_personal_access_token  # or: source a gitignored .env file first
   
   claude mcp add --transport stdio graphql-github \
     --env GRAPHQL_API_URL=https://api.github.com/graphql \
     --env GRAPHQL_INTROSPECTION_URL=https://api.github.com/graphql \
     --env GRAPHQL_TOKEN=$GH_TOKEN \
     --env GRAPHQL_INCLUDE_MUTATIONS=false \
     graphql-bridge -- mcp-graphql-bridge
   

   GRAPHQL_INCLUDE_MUTATIONS=false registers all 32 (read-only) queries and zero mutations — comfortably under the cap, and a meaningfully safer default for an AI agent than exposing all 252 write operations.

2. Ask Claude:

   Using graphql-github, look up the repository facebook/react and tell me its star count.

   Claude calls query__repository({ owner: "facebook", name: "react", __fields: "{ name stargazerCount }" }).

3. To also reach mutations, drop GRAPHQL_INCLUDE_MUTATIONS=false and raise the cap (GRAPHQL_MAX_TOOLS=400), understanding that this exposes write access to your GitHub account scoped to whatever permissions your token has.

Available tools

All per-operation tools accept a special __fields argument where you can provide a custom GraphQL selection set (e.g. { id name status }). If omitted, only scalar fields are returned.

Per-call auth override: every tool (including execute_graphql) also accepts bearer_token and custom_headers arguments. If provided, they override GRAPHQL_TOKEN/no-auth for that single request only, letting Claude switch credentials per call without restarting the server.

Security

• The target API is fixed per deployment, never a per-request parameter. Individual tool calls can override credentials (bearer_token, custom_headers) but never the destination host — GRAPHQL_API_URL is set once at deployment time. A shared server that let callers redirect it to an arbitrary destination would be a Server-Side Request Forgery (SSRF) primitive; this design rules that out by construction.
• Configured and per-call secrets are redacted from every response before it reaches the calling LLM.
• GRAPHQL_INCLUDE_MUTATIONS=false excludes every mutation field from registration for a genuinely read-only deployment — a meaningful trust boundary GraphQL's type system already encodes, rather than relying on token scope alone. This is enforced for execute_graphql too: it parses the query and rejects any mutation when this flag is off, rather than only omitting the convenience mutation__* tools while leaving the generic fallback able to run anything.
• MCP_AUTH_TOKEN gates the HTTP transport's /mcp endpoint for public-routable deployments; requests are capped at 10MB.

See docs/architecture.md for the full design rationale and SECURITY.md to report a vulnerability.

Docker

Build the image

docker build -t mcp-graphql-bridge .

Add to Claude Code via Docker

claude mcp add --transport stdio \
  --env GRAPHQL_API_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql \
  --env GRAPHQL_TOKEN=your-bearer-token \
  graphql-bridge -- docker run -i --rm \
  -e GRAPHQL_API_URL -e GRAPHQL_INTROSPECTION_URL -e GRAPHQL_TOKEN \
  mcp-graphql-bridge

Note: The -i flag (no -t) is required — it keeps stdin open for the MCP stdio protocol.

HTTP deployment

For hosted MCP access, run the HTTP transport instead of stdio:

docker build -f Dockerfile.http -t mcp-graphql-bridge-http .
docker run --rm -p 8080:8080 \
  -e GRAPHQL_API_URL=https://your-api.example.com/graphql \
  -e GRAPHQL_INTROSPECTION_URL=https://your-api.example.com/graphql \
  -e GRAPHQL_TOKEN=your-bearer-token \
  mcp-graphql-bridge-http

Health checks are available at /health; MCP requests are served at /mcp.

For public-routable deployments, set MCP_AUTH_TOKEN and configure clients to send Authorization: Bearer <token> to /mcp.

See docs/deployment.md for AWS, Cloudflare, and other container hosting options.

Development

npm run dev   # watch mode: rebuilds and restarts on file changes
npm run build # one-off TypeScript compile
npm start     # run the compiled server

Troubleshooting

Error: Cannot find module '.../index.js'

If you see an error like:

Error: Cannot find module '/path/to/mcp-graphql-bridge/index.js'

You are pointing to the wrong file. The TypeScript source must be compiled first, and the entry point is in the dist/ folder:

Correct path: /path/to/mcp-graphql-bridge/dist/index.js Wrong path: /path/to/mcp-graphql-bridge/index.js

Fix:

1. Ensure you ran npm run build (creates the dist/ folder)
2. Update your MCP configuration to use the full path ending in /dist/index.js

Schema introspection fails

If the server starts but shows "Schema introspection failed", your GraphQL API may have introspection disabled in production. Use the curl command in step 3 of Setup to pre-generate a schema-introspection.json file.

Tools not appearing in Claude Code

1. Run claude mcp list to verify the server is registered
2. Run /mcp in a Claude Code session to see available tools
3. Check that your GraphQL API's environment variables are set correctly (GRAPHQL_API_URL, GRAPHQL_INTROSPECTION_URL, GRAPHQL_TOKEN) — these are optional and default to a public demo API, so if tools still aren't appearing with your own API configured, check its credentials and endpoint URLs