Reddit MCP Server

Instructions

Implementation Reference

• src/index.ts:615-652 (handler)

  MCP tool handler for 'get_post_comments': extracts params, applies smart defaults, calls redditAPI.getPostComments, parses and validates response, formats comment tree with formatDataList and formatRedditComment, returns MCP-formatted text response.

  createToolHandler(async (params: z.infer<typeof SimplePostCommentsSchema>) => {
      const { post_id, sort } = params;
      
      // 🧠 Smart defaults for missing parameters
      const smartDefaults = getSmartDefaults(params, 'comments');
      const finalParams = { ...smartDefaults, post_id, sort: sort || smartDefaults.sort };
      
      const result = await redditAPI.getPostComments(post_id, finalParams.limit, finalParams.sort);
  
      if (!result.success) {
        return createErrorResponse("Error getting post comments", result.error);
      }
  
      const data = result.data;
      if (!data || !Array.isArray(data) || data.length === 0) {
        return createErrorResponse("No comments found for this post");
      }
  
      // The first element contains the post, the second contains comments
      const commentsData = data[1];
      if (!commentsData || !commentsData.data || !commentsData.data.children) {
        return createErrorResponse("No comments found for this post");
      }
  
      const comments = commentsData.data.children.map((child: any) => child.data);
      
      if (comments.length === 0) {
        return createSuccessResponse("No comments found for this post");
      }
  
      const summary = `💬 Found ${comments.length} comments for post ${post_id} (sorted by ${sort})`;
      
    // ✅ DRY: Sử dụng formatDataList helper
    const commentDetails = formatDataList(comments, formatRedditComment, COMMENT_PREVIEW_LIMIT, "comments");
  
    const resultText = `${summary}\n\n${commentDetails}`;
      return createSuccessResponse(resultText);
  })

• src/types/index.ts:118-121 (schema)

  Zod input schema defining required 'post_id' string and optional 'sort' enum (best, top, new) with defaults and descriptions.

  export const SimplePostCommentsSchema = z.object({
    post_id: z.string().describe("Reddit post ID to get comments for"),
    sort: z.enum(["best", "top", "new"]).default("best").describe("Sort order (default: best)")
  });

• src/index.ts:603-653 (registration)

  MCP server.tool registration for 'get_post_comments' including name, detailed description, input schema reference, and wrapped handler function.

  server.tool(
    "get_post_comments",
    "💬 Get comments for a Reddit post\n" +
    "🎯 What it does: Fetches comments and replies for any Reddit post\n" +
    "📝 Required: post_id (Reddit post ID, found in post URLs)\n" +
    "⚙️ Optional: sort ('best', 'top', 'new')\n" +
    "💡 Examples:\n" +
    "   • Get comments: {\"post_id\": \"1n1nlse\"}\n" +
    "   • Best comments: {\"post_id\": \"1n1nlse\", \"sort\": \"best\"}\n" +
    "   • New comments: {\"post_id\": \"1n1nlse\", \"sort\": \"new\"}\n" +
    "🔍 Output: Formatted comment tree with author, score, timestamp, and nested replies",
    SimplePostCommentsSchema.shape,
    createToolHandler(async (params: z.infer<typeof SimplePostCommentsSchema>) => {
        const { post_id, sort } = params;
        
        // 🧠 Smart defaults for missing parameters
        const smartDefaults = getSmartDefaults(params, 'comments');
        const finalParams = { ...smartDefaults, post_id, sort: sort || smartDefaults.sort };
        
        const result = await redditAPI.getPostComments(post_id, finalParams.limit, finalParams.sort);
  
        if (!result.success) {
          return createErrorResponse("Error getting post comments", result.error);
        }
  
        const data = result.data;
        if (!data || !Array.isArray(data) || data.length === 0) {
          return createErrorResponse("No comments found for this post");
        }
  
        // The first element contains the post, the second contains comments
        const commentsData = data[1];
        if (!commentsData || !commentsData.data || !commentsData.data.children) {
          return createErrorResponse("No comments found for this post");
        }
  
        const comments = commentsData.data.children.map((child: any) => child.data);
        
        if (comments.length === 0) {
          return createSuccessResponse("No comments found for this post");
        }
  
        const summary = `💬 Found ${comments.length} comments for post ${post_id} (sorted by ${sort})`;
        
      // ✅ DRY: Sử dụng formatDataList helper
      const commentDetails = formatDataList(comments, formatRedditComment, COMMENT_PREVIEW_LIMIT, "comments");
  
      const resultText = `${summary}\n\n${commentDetails}`;
        return createSuccessResponse(resultText);
    })
  );

• src/services/reddit-api.ts:395-406 (helper)

  Supporting method in RedditAPIService: constructs and executes authenticated GET request to Reddit API endpoint `/comments/{postId}.json` with limit/sort params, handles OAuth token, rate limits, errors, returns structured ApiCallResult.

  async getPostComments(
    postId: string,
    limit: number = 25,
    sort: "best" | "top" | "new" | "controversial" | "old" | "qa" = "best",
  ): Promise<ApiCallResult> {
    const params: Record<string, any> = { limit, sort };
  
    return this.makeRequest<Array<{ data: { children: Array<{ data: RedditComment }> } }>>(
      `/comments/${postId}.json`,
      params,
    );
  }