MCP Hacker News

Instructions

Implementation Reference

• src/tools.ts:556-586 (handler)

  The execute handler function for the 'getUpdates' MCP tool. It fetches recent updates from the Hacker News '/updates' endpoint, handles errors, limits results to top 10 items and profiles, and returns a standardized MCP content response with JSON text.

  execute: async (args: any) => {
    const updates = await fetchFromAPI<HackerNewsUpdates>("/updates");
  
    if (!updates) {
      return {
        content: [
          {
            type: "text",
            text: JSON.stringify({ error: "Failed to fetch updates" }),
          },
        ],
      };
    }
  
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(
            {
              message: "Recent updates",
              recentlyUpdatedItems: updates.items.slice(0, 10),
              recentlyUpdatedProfiles: updates.profiles.slice(0, 10),
            },
            null,
            2
          ),
        },
      ],
    };
  },

• src/tools.ts:555-555 (schema)

  Input schema definition for the 'getUpdates' tool, specifying no required parameters.

  inputSchema: { type: "object", properties: {} },

• src/index.ts:52-65 (registration)

  MCP 'tools/call' request handler in the main server that locates the 'getUpdates' tool by name from the tools array and invokes its execute method with arguments.

  if (json.method === "tools/call") {
    const tool = tools.find((tool) => tool.name === json.params.name);
    if (tool) {
      const toolResponse = await tool.execute(json.params.arguments);
      sendResponse(json.id, toolResponse);
    } else {
      sendResponse(json.id, {
        error: {
          code: -32602,
          message: `MCP error -32602: Tool ${json.params.name} not found`,
        },
      });
    }
  }

• src/fetch-actions.ts:9-26 (helper)

  fetchFromAPI utility function called by the getUpdates handler to retrieve data from the Hacker News API (used with endpoint '/updates'), including caching via helpers.

  export async function fetchFromAPI<T>(endpoint: string): Promise<T | null> {
    const cacheKey = endpoint;
    const cached = getCached<T>(cacheKey);
    if (cached) return cached;
  
    try {
      const response = await fetch(
        `https://hacker-news.firebaseio.com/v0${endpoint}.json`
      );
      if (!response.ok) throw new Error(`HTTP ${response.status}`);
  
      const data = await response.json();
      setCache(cacheKey, data);
      return data;
    } catch (error) {
      console.error(`Error fetching ${endpoint}:`, error);
      return null;
    }

• src/types-hn.ts:31-34 (schema)

  TypeScript interface defining the structure of updates data returned by the Hacker News '/updates' endpoint, used in the handler's type annotation.

  export interface HackerNewsUpdates {
    items: number[];
    profiles: string[];
  }