Reddit MCP Server

Instructions

Implementation Reference

• src/index.ts:671-710 (handler)

  The core execution logic of the get_trending_subreddits tool handler. It applies smart defaults, calls the Reddit API service to fetch trending subreddits, validates the response, creates a custom formatter for subreddits, uses formatDataList helper to preview limited results, and returns a formatted markdown text response via createSuccessResponse.

  createToolHandler(async (params: z.infer<typeof SimpleTrendingSubredditsSchema>) => {
      // 🧠 Smart defaults - no parameters needed
      const smartDefaults = getSmartDefaults(params, 'trending');
      const finalParams = { ...smartDefaults };
      
      const result = await redditAPI.getTrendingSubreddits(finalParams.limit || 25);
  
    // ✅ DRY: Sử dụng validateApiResponse helper
    const subreddits = validateApiResponse(result, "trending subreddits");
      
      if (subreddits.length === 0) {
        return createSuccessResponse("No trending subreddits found");
      }
  
      const summary = `🔥 Found ${subreddits.length} trending subreddits`;
      
    // ✅ DRY: Sử dụng formatDataList helper với custom formatter
    const subredditFormatter = (subreddit: any) => {
        const name = subreddit.display_name || 'Unknown';
        const title = subreddit.title || 'No title';
        const subscribers = subreddit.subscribers || 0;
        const description = subreddit.public_description || 'No description';
        
        let result = `🏠 **r/${name}** - ${title}\n`;
        result += `👥 ${subscribers.toLocaleString()} subscribers\n`;
        if (description.length > 100) {
          result += `📄 ${description.substring(0, 100)}...\n`;
        } else {
          result += `📄 ${description}\n`;
        }
        result += `🔗 https://reddit.com/r/${name}\n`;
        
        return result;
    };
    
    const subredditDetails = formatDataList(subreddits, subredditFormatter, TRENDING_SUBREDDIT_LIMIT, "subreddits");
  
    const resultText = `${summary}\n\n${subredditDetails}`;
    return createSuccessResponse(resultText);
  })

• src/index.ts:661-712 (registration)

  MCP server tool registration for 'get_trending_subreddits'. Registers the tool with name, detailed usage description including examples, input schema reference, and the wrapped handler function using createToolHandler.

  server.tool(
    "get_trending_subreddits",
    "🔥 Get trending/popular subreddits\n" +
    "🎯 What it does: Fetches list of currently popular and trending subreddits\n" +
    "📝 Required: None (no parameters needed)\n" +
    "💡 Examples:\n" +
    "   • Get trending: {}\n" +
    "   • Simple call: {}\n" +
    "🔍 Output: List of trending subreddits with name, title, subscribers, description, and URL",
    SimpleTrendingSubredditsSchema.shape,
    createToolHandler(async (params: z.infer<typeof SimpleTrendingSubredditsSchema>) => {
        // 🧠 Smart defaults - no parameters needed
        const smartDefaults = getSmartDefaults(params, 'trending');
        const finalParams = { ...smartDefaults };
        
        const result = await redditAPI.getTrendingSubreddits(finalParams.limit || 25);
  
      // ✅ DRY: Sử dụng validateApiResponse helper
      const subreddits = validateApiResponse(result, "trending subreddits");
        
        if (subreddits.length === 0) {
          return createSuccessResponse("No trending subreddits found");
        }
  
        const summary = `🔥 Found ${subreddits.length} trending subreddits`;
        
      // ✅ DRY: Sử dụng formatDataList helper với custom formatter
      const subredditFormatter = (subreddit: any) => {
          const name = subreddit.display_name || 'Unknown';
          const title = subreddit.title || 'No title';
          const subscribers = subreddit.subscribers || 0;
          const description = subreddit.public_description || 'No description';
          
          let result = `🏠 **r/${name}** - ${title}\n`;
          result += `👥 ${subscribers.toLocaleString()} subscribers\n`;
          if (description.length > 100) {
            result += `📄 ${description.substring(0, 100)}...\n`;
          } else {
            result += `📄 ${description}\n`;
          }
          result += `🔗 https://reddit.com/r/${name}\n`;
          
          return result;
      };
      
      const subredditDetails = formatDataList(subreddits, subredditFormatter, TRENDING_SUBREDDIT_LIMIT, "subreddits");
  
      const resultText = `${summary}\n\n${subredditDetails}`;
      return createSuccessResponse(resultText);
    })
  );

• src/types/index.ts:124-124 (schema)

  Zod input schema for the get_trending_subreddits tool. Defined as an empty object since the tool requires no parameters, allowing parameterless calls.

  export const SimpleTrendingSubredditsSchema = z.object({});

• src/services/reddit-api.ts:411-416 (helper)

  Supporting API service method in RedditAPIService that performs the authenticated GET request to Reddit's /subreddits/popular.json endpoint to retrieve the list of popular/trending subreddits, handling OAuth, rate limiting, and error responses.

  async getTrendingSubreddits(limit: number = 25): Promise<ApiCallResult> {
    return this.makeRequest<{ data: { children: Array<{ data: RedditSubreddit }> } }>(
      "/subreddits/popular.json",
      { limit },
    );
  }