Reddit MCP Server

Instructions

Implementation Reference

• src/reddit-client.ts:139-148 (handler)

  Core handler function that fetches comments from Reddit API for a given post, extracts them recursively, and returns a flat list of RedditComment objects.

  async getPostComments(postId: string, sort: 'best' | 'top' | 'new' | 'controversial' | 'old' = 'best'): Promise<RedditComment[]> {
    const data = await this.makeRequest(`/comments/${postId}?sort=${sort}`);
    const comments: RedditComment[] = [];
    
    if (data[1] && data[1].data && data[1].data.children) {
      this.extractComments(data[1].data.children, comments);
    }
    
    return comments;
  }

• src/index.ts:322-333 (handler)

  MCP CallToolRequest handler case that validates input using Zod schema and delegates execution to RedditClient.getPostComments, formatting response as JSON text.

  case 'get_post_comments': {
    const args = GetPostCommentsSchema.parse(request.params.arguments);
    const comments = await redditClient.getPostComments(args.postId, args.sort);
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(comments, null, 2),
        },
      ],
    };
  }

• src/index.ts:48-51 (schema)

  Zod schema defining and validating the tool's input parameters: postId (required string) and sort (enum with default 'best'). Used for parsing in handler.

  const GetPostCommentsSchema = z.object({
    postId: z.string().min(1, "Post ID is required"),
    sort: z.enum(['best', 'top', 'new', 'controversial', 'old']).default('best'),
  });

• src/index.ts:130-149 (registration)

  Tool registration in ListTools response, specifying name, description, and JSON inputSchema advertised to MCP clients.

  {
    name: 'get_post_comments',
    description: 'Get comments from a Reddit post',
    inputSchema: {
      type: 'object',
      properties: {
        postId: {
          type: 'string',
          description: 'Reddit post ID',
        },
        sort: {
          type: 'string',
          enum: ['best', 'top', 'new', 'controversial', 'old'],
          description: 'Sort order for comments',
          default: 'best',
        },
      },
      required: ['postId'],
    },
  },

• src/reddit-client.ts:190-198 (helper)

  Recursive helper function to traverse Reddit's nested comment tree and collect all top-level and reply comments into a flat array.

  private extractComments(children: any[], comments: RedditComment[]): void {
    for (const child of children) {
      if (child.kind === 't1' && child.data) {
        comments.push(this.mapComment(child.data));
        if (child.data.replies && child.data.replies.data && child.data.replies.data.children) {
          this.extractComments(child.data.replies.data.children, comments);
        }
      }
    }