reddit-mcp-server

Instructions

Implementation Reference

• src/index.ts:497-532 (registration)

  MCP tool registration for 'create_post', including schema and inline handler function

  server.addTool({
    name: "create_post",
    description: "Create a new post in a subreddit (requires REDDIT_USERNAME and REDDIT_PASSWORD)",
    parameters: z.object({
      subreddit: z.string().describe("The subreddit name (without r/ prefix)"),
      title: z.string().describe("The post title"),
      content: z.string().describe("The post content (text for self posts, URL for link posts)"),
      is_self: z.boolean().default(true).describe("Whether this is a self post (text) or link post"),
    }),
    execute: async (args) => {
      const client = getRedditClient()
      if (!client) {
        throw new Error("Reddit client not initialized")
      }
  
      // Check if user credentials are configured
      if (!process.env.REDDIT_USERNAME || !process.env.REDDIT_PASSWORD) {
        throw new Error(
          "User authentication required. Please set REDDIT_USERNAME and REDDIT_PASSWORD environment variables.",
        )
      }
  
      const post = await client.createPost(args.subreddit, args.title, args.content, args.is_self)
      const formattedPost = formatPostInfo(post)
  
      return `# Post Created Successfully
  
  ## Post Details
  - Title: ${formattedPost.title}
  - Subreddit: r/${formattedPost.subreddit}
  - Type: ${formattedPost.type}
  - Link: ${formattedPost.links.fullPost}
  
  Your post has been successfully submitted to r/${formattedPost.subreddit}.`
    },
  })

• src/client/reddit-client.ts:295-356 (handler)

  Core handler in RedditClient that performs the actual POST /api/submit to Reddit API

  async createPost(subreddit: string, title: string, content: string, isSelf: boolean = true): Promise<RedditPost> {
    await this.authenticate()
  
    if (!this.username || !this.password) {
      throw new Error("User authentication required for posting")
    }
  
    try {
      const kind = isSelf ? "self" : "link"
      const params = new URLSearchParams()
      params.append("sr", subreddit)
      params.append("kind", kind)
      params.append("title", title)
      params.append(isSelf ? "text" : "url", content)
      params.append("api_type", "json") // Request standard JSON response format
  
      const response = await this.makeRequest("/api/submit", {
        method: "POST",
        headers: {
          "Content-Type": "application/x-www-form-urlencoded",
        },
        body: params.toString(),
      })
  
      if (!response.ok) {
        const errorText = await response.text()
        console.error(`[Reddit API] Create post failed: ${response.status} ${response.statusText}`)
        console.error(`[Reddit API] Error response: ${errorText}`)
        throw new Error(`HTTP ${response.status}: ${errorText}`)
      }
  
      const json = (await response.json()) as any
      console.error(`[Reddit API] Create post response:`, JSON.stringify(json, null, 2))
  
      // With api_type=json, response has json.data.id or json.errors
      if (json.json?.errors && json.json.errors.length > 0) {
        const errors = json.json.errors.map((e: any) => e.join(": ")).join(", ")
        console.error(`[Reddit API] Post creation errors: ${errors}`)
        throw new Error(`Reddit API errors: ${errors}`)
      }
  
      // Extract post ID from standard JSON response
      const postId = json.json?.data?.id || json.json?.data?.name?.replace("t3_", "")
  
      if (!postId) {
        console.error(`[Reddit API] No post ID in response`)
        throw new Error("No post ID returned from Reddit")
      }
  
      console.error(`[Reddit API] Post created with ID: ${postId}`)
      return await this.getPost(postId, subreddit)
    } catch (error) {
      // Log and re-throw the actual error
      console.error(`[Reddit API] Create post exception:`, error)
      if (error instanceof Error && error.message.includes("HTTP")) {
        throw error
      }
      throw new Error(
        `Failed to create post in ${subreddit}: ${error instanceof Error ? error.message : String(error)}`,
      )
    }
  }

• src/index.ts:500-505 (schema)

  Input schema validation using Zod for the create_post tool parameters

  parameters: z.object({
    subreddit: z.string().describe("The subreddit name (without r/ prefix)"),
    title: z.string().describe("The post title"),
    content: z.string().describe("The post content (text for self posts, URL for link posts)"),
    is_self: z.boolean().default(true).describe("Whether this is a self post (text) or link post"),
  }),