Fitbit MCP Server

Instructions

Implementation Reference

• src/nutrition.ts:102-132 (handler)

  The async handler function for the 'get_food_log' tool. It constructs the Fitbit API endpoint for food log on the specified date, fetches the data using makeFitbitRequest, handles errors, and returns the JSON response.

  async ({
    date = 'today',
  }: FoodLogParams): Promise<ToolResponseStructure> => {
    // Construct the endpoint
    const endpoint = `foods/log/date/${date}.json`;
  
    const foodLogData = await makeFitbitRequest<FoodLogResponse>(
      endpoint,
      getAccessTokenFn,
      FITBIT_API_BASE
    );
  
    // Handle API call failure
    if (!foodLogData) {
      return {
        content: [
          {
            type: 'text',
            text: `Failed to retrieve food log data from Fitbit API for date '${date}'. Check token and permissions.`,
          },
        ],
        isError: true,
      };
    }
  
    // Return successful response with raw JSON
    const rawJsonResponse = JSON.stringify(foodLogData, null, 2);
    return {
      content: [{ type: 'text', text: rawJsonResponse }],
    };
  }

• src/nutrition.ts:81-92 (schema)

  Zod schema defining the input parameters for the 'get_food_log' tool, specifically the optional 'date' parameter.

  const foodLogParametersSchemaShape = {
    date: z
      .string()
      .regex(
        /^\d{4}-\d{2}-\d{2}$|^today$/,
        "Date must be in YYYY-MM-DD format or 'today'."
      )
      .optional()
      .describe(
        "The date for which to retrieve food log data (YYYY-MM-DD or 'today'). Defaults to 'today'."
      ),
  };

• src/nutrition.ts:98-133 (registration)

  Registers the 'get_food_log' tool on the MCP server using server.tool(), providing name, description, input schema, and handler function.

  server.tool(
    foodLogToolName,
    foodLogDescription,
    foodLogParametersSchemaShape,
    async ({
      date = 'today',
    }: FoodLogParams): Promise<ToolResponseStructure> => {
      // Construct the endpoint
      const endpoint = `foods/log/date/${date}.json`;
  
      const foodLogData = await makeFitbitRequest<FoodLogResponse>(
        endpoint,
        getAccessTokenFn,
        FITBIT_API_BASE
      );
  
      // Handle API call failure
      if (!foodLogData) {
        return {
          content: [
            {
              type: 'text',
              text: `Failed to retrieve food log data from Fitbit API for date '${date}'. Check token and permissions.`,
            },
          ],
          isError: true,
        };
      }
  
      // Return successful response with raw JSON
      const rawJsonResponse = JSON.stringify(foodLogData, null, 2);
      return {
        content: [{ type: 'text', text: rawJsonResponse }],
      };
    }
  );

• src/utils.ts:37-83 (helper)

  Shared helper function used by the handler to make authenticated requests to the Fitbit API.

  export async function makeFitbitRequest<T>(
    endpoint: string,
    getAccessTokenFn: () => Promise<string | null>,
    apiBase: string = FITBIT_API_VERSIONS.V1
  ): Promise<T | null> {
    const currentAccessToken = await getAccessTokenFn();
    if (!currentAccessToken) {
      console.error(`Error: ${ERROR_MESSAGES.NO_ACCESS_TOKEN}`);
      return null;
    }
  
    // Ensure endpoint starts correctly relative to the user path
    const cleanEndpoint = endpoint.startsWith('/')
      ? endpoint.substring(1)
      : endpoint;
    // Construct the full URL including the user scope '-'.
    const url = `${apiBase}/user/-/${cleanEndpoint}`;
    console.error(`Attempting Fitbit API request to: ${url}`);
  
    const headers = {
      'User-Agent': HTTP_CONFIG.USER_AGENT,
      Authorization: `Bearer ${currentAccessToken}`,
      Accept: 'application/json',
    };
  
    try {
      const response = await fetch(url, { headers });
      if (!response.ok) {
        const errorBody = await response.text();
        console.error(
          `Fitbit API Error! Status: ${response.status}, URL: ${url}, Body: ${errorBody}`
        );
        if (response.status === 401) {
          console.error(ERROR_MESSAGES.TOKEN_EXPIRED);
        }
        return null;
      }
      // Handle potential empty response body for certain success statuses (e.g., 204 No Content)
      if (response.status === 204) {
        return {} as T; // Return an empty object or appropriate type for no content
      }
      return (await response.json()) as T;
    } catch (error) {
      console.error(`Error making Fitbit request to ${url}:`, error);
      return null;
    }
  }

• src/index.ts:82-82 (registration)

  Top-level call to registerNutritionTools, which includes the registration of 'get_food_log'.

  registerNutritionTools(server, getAccessToken);