substack-mcp

Instructions

Implementation Reference

• src/server.ts:149-162 (handler)

  The handler function for get_post_comments tool. Calls the API client to fetch comments, then maps the response to extract id, name, body, date, reactions, and replies count, returning the result as formatted JSON.

  async ({ post_id, limit }) => {
    const comments = await client.getPostComments(post_id, limit);
    const summary = comments.map((c) => ({
      id: c.id,
      name: c.name,
      body: c.body,
      date: c.date,
      reactions: c.reactions,
      replies: c.children_count,
    }));
    return {
      content: [{ type: "text", text: JSON.stringify(summary, null, 2) }],
    };
  },

• src/server.ts:142-163 (registration)

  Registration of the get_post_comments tool with MCP server. Defines the tool name, description, input schema (post_id as number, limit as optional number with default 20), and the handler function.

  server.tool(
    "get_post_comments",
    "Get comments on a published post. Returns commenter name, comment body, date, and reaction counts.",
    {
      post_id: z.number().describe("The post ID to get comments for"),
      limit: z.number().optional().default(20).describe("Max comments to return (default 20)"),
    },
    async ({ post_id, limit }) => {
      const comments = await client.getPostComments(post_id, limit);
      const summary = comments.map((c) => ({
        id: c.id,
        name: c.name,
        body: c.body,
        date: c.date,
        reactions: c.reactions,
        replies: c.children_count,
      }));
      return {
        content: [{ type: "text", text: JSON.stringify(summary, null, 2) }],
      };
    },
  );

• src/api/client.ts:171-180 (helper)

  API client method getPostComments that fetches comments from the Substack API endpoint /api/v1/post/{postId}/comments. Returns an array of SubstackComment objects, sliced to the specified limit.

  async getPostComments(
    postId: number,
    limit = 20,
  ): Promise<SubstackComment[]> {
    const data = await this.request<{ comments: SubstackComment[] }>(
      `${this.publicationUrl}/api/v1/post/${postId}/comments`,
    );
    const comments = data.comments || [];
    return comments.slice(0, limit);
  }

• src/api/types.ts:81-91 (schema)

  TypeScript interface SubstackComment defining the structure of comment objects returned by the API. Includes id, body, name, date, user_id, optional reactions map, and children_count for replies.

  export interface SubstackComment {
    id: number;
    body: string;
    body_json?: unknown;
    name: string;
    date: string;
    user_id: number;
    author_is_admin?: boolean;
    reactions?: Record<string, number>;
    children_count?: number;
  }