Farcaster MCP Server

Instructions

Implementation Reference

• src/index.ts:421-465 (handler)

  The async handler function that implements the core logic of the 'get-user-casts' tool: fetches casts for a given FID from the Hubble API, formats them using formatCasts helper, and returns formatted text response or error.

  async ({ fid, limit = 10 }: { fid: number; limit?: number }) => {
    try {
      console.error(`Fetching casts for FID ${fid} with limit ${limit}`);
      const response = await fetchFromHubble(`/castsByFid`, {
        fid,
        pageSize: limit,
        reverse: 1 // Get newest first
      }) as FarcasterCastsResponse;
      
      console.error(`Got response with ${response.messages?.length || 0} messages`);
      
      if (!response.messages || response.messages.length === 0) {
        return {
          content: [
            {
              type: "text",
              text: `No casts found for FID ${fid}`
            }
          ]
        };
      }
      
      const castsText = await formatCasts(response.messages, limit);
      
      return {
        content: [
          {
            type: "text",
            text: `# Casts from FID ${fid}\n\n${castsText}`
          }
        ]
      };
    } catch (error) {
      console.error("Error in get-user-casts:", error);
      return {
        content: [
          {
            type: "text",
            text: `Error fetching casts: ${error instanceof Error ? error.message : String(error)}`
          }
        ],
        isError: true
      };
    }
  }

• src/index.ts:417-420 (schema)

  Zod schema defining input parameters for the 'get-user-casts' tool: required fid (number) and optional limit (number).

  {
    fid: z.number().describe("Farcaster user ID (FID)"),
    limit: z.number().optional().describe("Maximum number of casts to return (default: 10)")
  },

• src/index.ts:414-466 (registration)

  Registration of the 'get-user-casts' tool with MCP server using server.tool(name, description, inputSchema, handler).

  server.tool(
    "get-user-casts",
    "Get casts from a specific Farcaster user by FID",
    {
      fid: z.number().describe("Farcaster user ID (FID)"),
      limit: z.number().optional().describe("Maximum number of casts to return (default: 10)")
    },
    async ({ fid, limit = 10 }: { fid: number; limit?: number }) => {
      try {
        console.error(`Fetching casts for FID ${fid} with limit ${limit}`);
        const response = await fetchFromHubble(`/castsByFid`, {
          fid,
          pageSize: limit,
          reverse: 1 // Get newest first
        }) as FarcasterCastsResponse;
        
        console.error(`Got response with ${response.messages?.length || 0} messages`);
        
        if (!response.messages || response.messages.length === 0) {
          return {
            content: [
              {
                type: "text",
                text: `No casts found for FID ${fid}`
              }
            ]
          };
        }
        
        const castsText = await formatCasts(response.messages, limit);
        
        return {
          content: [
            {
              type: "text",
              text: `# Casts from FID ${fid}\n\n${castsText}`
            }
          ]
        };
      } catch (error) {
        console.error("Error in get-user-casts:", error);
        return {
          content: [
            {
              type: "text",
              text: `Error fetching casts: ${error instanceof Error ? error.message : String(error)}`
            }
          ],
          isError: true
        };
      }
    }
  );