GrowthBook MCP Server

Instructions

Implementation Reference

• src/tools/features.ts:40-129 (handler)

  The handler function that executes the create_feature_flag tool: fetches environments, constructs payload, posts to GrowthBook API, handles response, and returns formatted content with links and code stubs.
  async ({ id, valueType, defaultValue, description, project, fileExtension, }) => { // get environments let environments = []; const defaults = await getDefaults(apiKey, baseApiUrl); if (defaults.environments) { environments = defaults.environments; } else { const envRes = await fetch( `${baseApiUrl}/api/v1/features/environments`, { headers: { Authorization: `Bearer ${apiKey}`, "Content-Type": "application/json", }, } ); await handleResNotOk(envRes); const envData = await envRes.json(); environments = envData.environments.map((env: any) => env.id); } const payload = { id, description, owner: user, valueType, defaultValue, tags: ["mcp"], environments: environments.reduce( (acc: Record<string, any>, env: string) => { acc[env] = { enabled: false, rules: [], }; return acc; }, {} ), ...(project && { project }), }; try { const res = await fetch(`${baseApiUrl}/api/v1/features`, { method: "POST", headers: { Authorization: `Bearer ${apiKey}`, "Content-Type": "application/json", }, body: JSON.stringify(payload), }); await handleResNotOk(res); const data = await res.json(); const { docs, language, stub } = getDocsMetadata(fileExtension); const linkToGrowthBook = generateLinkToGrowthBook( appOrigin, "features", id ); const text = `This is the API response: ${JSON.stringify(data, null, 2)} Additionally, here is a template of what to show to the user: **✅ Your feature flag \`my-flag-name\` is ready!** [View it in GrowthBook](${linkToGrowthBook}) **How to use it in your code:** (To the LLM agent. Use the text below to properly add the feature flag to the codebase. Also, surface the relevant docs/implemenation to the user) ${stub} **Want to learn more?** See the [GrowthBook ${language} docs](${docs}) `; return { content: [{ type: "text", text }], }; } catch (error) { throw new Error(`Error creating feature flag: ${error}`); } }
• src/tools/features.ts:22-130 (registration)

  Registers the create_feature_flag tool on the MCP server within registerFeatureTools, specifying name, description, input schema, hints, and handler function.
  /** * Tool: create_feature_flag */ server.tool( "create_feature_flag", "Creates a new feature flag in GrowthBook and modifies the codebase when relevant.", { id: featureFlagSchema.id, valueType: featureFlagSchema.valueType, defaultValue: featureFlagSchema.defaultValue, description: featureFlagSchema.description.optional().default(""), project: featureFlagSchema.project.optional(), fileExtension: featureFlagSchema.fileExtension, }, { readOnlyHint: false, destructiveHint: false, }, async ({ id, valueType, defaultValue, description, project, fileExtension, }) => { // get environments let environments = []; const defaults = await getDefaults(apiKey, baseApiUrl); if (defaults.environments) { environments = defaults.environments; } else { const envRes = await fetch( `${baseApiUrl}/api/v1/features/environments`, { headers: { Authorization: `Bearer ${apiKey}`, "Content-Type": "application/json", }, } ); await handleResNotOk(envRes); const envData = await envRes.json(); environments = envData.environments.map((env: any) => env.id); } const payload = { id, description, owner: user, valueType, defaultValue, tags: ["mcp"], environments: environments.reduce( (acc: Record<string, any>, env: string) => { acc[env] = { enabled: false, rules: [], }; return acc; }, {} ), ...(project && { project }), }; try { const res = await fetch(`${baseApiUrl}/api/v1/features`, { method: "POST", headers: { Authorization: `Bearer ${apiKey}`, "Content-Type": "application/json", }, body: JSON.stringify(payload), }); await handleResNotOk(res); const data = await res.json(); const { docs, language, stub } = getDocsMetadata(fileExtension); const linkToGrowthBook = generateLinkToGrowthBook( appOrigin, "features", id ); const text = `This is the API response: ${JSON.stringify(data, null, 2)} Additionally, here is a template of what to show to the user: **✅ Your feature flag \`my-flag-name\` is ready!** [View it in GrowthBook](${linkToGrowthBook}) **How to use it in your code:** (To the LLM agent. Use the text below to properly add the feature flag to the codebase. Also, surface the relevant docs/implemenation to the user) ${stub} **Want to learn more?** See the [GrowthBook ${language} docs](${docs}) `; return { content: [{ type: "text", text }], }; } catch (error) { throw new Error(`Error creating feature flag: ${error}`); } } );
• src/utils.ts:240-263 (schema)

  Shared Zod schema object defining input parameters for feature flag tools, including id, valueType, defaultValue, etc.
  export const featureFlagSchema = { id: z .string() .regex( /^[a-zA-Z0-9_.:|_-]+$/, "Feature key can only include letters, numbers, and the characters _, -, ., :, and |" ) .describe("A unique key name for the feature"), valueType: z .enum(["string", "number", "boolean", "json"]) .describe("The value type the feature flag will return"), defaultValue: z.string().describe("The default value of the feature flag"), description: z.string().describe("A brief description of the feature flag"), archived: z.boolean().describe("Whether the feature flag should be archived"), project: z .string() .describe("The ID of the project to which the feature flag belongs"), // Contextual info fileExtension: z .enum(SUPPORTED_FILE_EXTENSIONS) .describe( "The extension of the current file. If it's unclear, ask the user." ), } as const;
• src/index.ts:81-87 (registration)

  Top-level call to registerFeatureTools in the main MCP server initialization, which includes the create_feature_flag tool.
  registerFeatureTools({ server, baseApiUrl, apiKey, appOrigin, user, });