Growthbook MCP

What growthbook/growthbook-mcp MCP server does

The growthbook/growthbook-mcp MCP server gives an MCP client access to GrowthBook’s REST API and bundled agent skills. It is intended for tasks involving GrowthBook feature flags, experiments, and related API resources. The server does not provide a separate formatter for each endpoint; agents send requests to the GrowthBook REST API and receive the raw response body for successful calls.

The repository describes a thin server whose task-specific knowledge comes from a skills collection bundled during the build. Skills provide workflows and guardrails, while the API tool performs the requests those workflows describe. This keeps the server focused on exposing GrowthBook operations rather than implementing a separate abstraction for every API resource.

How it works

An agent can first call growthbook_list_skills to see available top-level workflows. It can then use growthbook_read_skill to load a complete workflow or a qualified child workflow, such as a feature-flag creation reference. The workflow may describe commands such as gb-call GET /api/v1/projects; the MCP server maps those instructions to its GrowthBook API request capability instead of executing the shell command.

Read operations use GET requests. Write operations use POST, PUT, PATCH, or DELETE requests and may include a JSON body. The server distinguishes read and write capabilities so MCP clients can identify read-only and potentially destructive actions. Agents should obtain confirmation before a mutation unless the user has already explicitly requested it.

The server defaults to stdio. It can also run as a standalone HTTP service with MCP endpoints at /mcp and /mcp/api. The full endpoint exposes skills and API operations, while the capability-only endpoint exposes API read and write operations.

Setup and configuration

Install dependencies and build the project with:

npm install
npm run build

A published release can be started with npx @growthbook/mcp. For stdio, configure the MCP client to run the package or the compiled Node entrypoint and provide GB_API_KEY. This value can be a GrowthBook API key or personal access token. GB_API_URL defaults to https://api.growthbook.io and can point to a self-hosted GrowthBook installation.

Set GB_MCP_TRANSPORT=http for HTTP mode. HTTP mode requires GB_MCP_URL, which identifies the public MCP base URL used in OAuth resource metadata. GB_MCP_PORT defaults to 3333, and GB_MCP_HOST defaults to 127.0.0.1. GB_OAUTH_ISSUER can override the OAuth issuer, which otherwise follows GB_API_URL.

Tools and capabilities

• List available GrowthBook skills and their descriptions.
• Read full skill workflows and qualified child references.
• Send authenticated GET requests to GrowthBook REST API paths.
• Send authenticated POST, PUT, PATCH, and DELETE requests with optional JSON bodies.
• Disable skill tools with GB_SKILLS_ENABLED=false or 0 when only API access is needed.
• Add extra request headers through variables prefixed with GB_HTTP_HEADER_.

The growthbook/growthbook-mcp MCP server returns actionable errors for non-successful API responses, including authentication failures, rate limits, and some self-hosted API path issues. In HTTP mode, rejected bearer tokens are surfaced as HTTP 401 responses so clients can refresh them; a 403 is treated as an accepted token with insufficient permission.

Limitations and notes

The server depends on access to a GrowthBook API and valid credentials for authenticated use. Skill content is bundled at build time from the canonical skills repository, with the selected commit controlled by the project’s lock file. Local builds can use a configured skills checkout, so the available workflows may depend on the build source.

The growthbook/growthbook-mcp MCP server does not execute the gb-call shell adapter referenced by skill documentation. Agents must translate those instructions into the MCP API request tool. HTTP deployments intended for public or multi-tenant use should be placed behind the deployer’s own gateway or authentication controls.