GrowthBook MCP Server

Instructions

Implementation Reference

• src/tools/features.ts:155-221 (handler)

  The handler function that implements the create_force_rule tool. It fetches default environments, constructs a payload with force rules for each environment, sends a POST request to update the feature flag, handles the response, and returns formatted content with GrowthBook link and code stub.

  async ({ featureId, description, condition, value, fileExtension }) => {
    try {
      // Fetch feature defaults first and surface to user
      const defaults = await getDefaults(apiKey, baseApiUrl);
      const defaultEnvironments = defaults.environments;
  
      const payload = {
        // Loop through the environments and create a rule for each one keyed by environment name
        environments: defaultEnvironments.reduce((acc, env) => {
          acc[env] = {
            enabled: false,
            rules: [
              {
                type: "force",
                description,
                condition,
                value,
              },
            ],
          };
          return acc;
        }, {} as Record<string, { enabled: boolean; rules: Array<any> }>),
      };
  
      const res = await fetch(`${baseApiUrl}/api/v1/features/${featureId}`, {
        method: "POST",
        headers: {
          Authorization: `Bearer ${apiKey}`,
          "Content-Type": "application/json",
        },
        body: JSON.stringify(payload),
      });
  
      await handleResNotOk(res);
  
      const data = await res.json();
  
      const linkToGrowthBook = generateLinkToGrowthBook(
        appOrigin,
        "features",
        featureId
      );
      const { docs, language, stub } = getDocsMetadata(fileExtension);
  
      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 force rule: ${error}`);
    }
  }

• src/tools/features.ts:138-151 (schema)

  Input schema for the create_force_rule tool, defining parameters like featureId, description, fileExtension, condition, and value using Zod.

  {
    featureId: featureFlagSchema.id,
    description: featureFlagSchema.description.optional().default(""),
    fileExtension: featureFlagSchema.fileExtension,
    condition: z
      .string()
      .describe(
        "Applied to everyone by default. Write conditions in MongoDB-style query syntax."
      )
      .optional(),
    value: z
      .string()
      .describe("The type of the value should match the feature type"),
  },

• src/tools/features.ts:132-222 (registration)

  Registration of the create_force_rule tool using server.tool, including description, schema, hints, and handler reference.

  /**
   * Tool: create_force_rule
   */
  server.tool(
    "create_force_rule",
    "Create a new force rule on an existing feature. If the existing feature isn't apparent, create a new feature using create_feature_flag first. A force rule sets a feature to a specific value based on a condition. For A/B tests and experiments, use create_experiment instead.",
    {
      featureId: featureFlagSchema.id,
      description: featureFlagSchema.description.optional().default(""),
      fileExtension: featureFlagSchema.fileExtension,
      condition: z
        .string()
        .describe(
          "Applied to everyone by default. Write conditions in MongoDB-style query syntax."
        )
        .optional(),
      value: z
        .string()
        .describe("The type of the value should match the feature type"),
    },
    {
      readOnlyHint: false,
    },
    async ({ featureId, description, condition, value, fileExtension }) => {
      try {
        // Fetch feature defaults first and surface to user
        const defaults = await getDefaults(apiKey, baseApiUrl);
        const defaultEnvironments = defaults.environments;
  
        const payload = {
          // Loop through the environments and create a rule for each one keyed by environment name
          environments: defaultEnvironments.reduce((acc, env) => {
            acc[env] = {
              enabled: false,
              rules: [
                {
                  type: "force",
                  description,
                  condition,
                  value,
                },
              ],
            };
            return acc;
          }, {} as Record<string, { enabled: boolean; rules: Array<any> }>),
        };
  
        const res = await fetch(`${baseApiUrl}/api/v1/features/${featureId}`, {
          method: "POST",
          headers: {
            Authorization: `Bearer ${apiKey}`,
            "Content-Type": "application/json",
          },
          body: JSON.stringify(payload),
        });
  
        await handleResNotOk(res);
  
        const data = await res.json();
  
        const linkToGrowthBook = generateLinkToGrowthBook(
          appOrigin,
          "features",
          featureId
        );
        const { docs, language, stub } = getDocsMetadata(fileExtension);
  
        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 force rule: ${error}`);
      }
    }
  );