posterly

MCP connector

Mastodon MCP server

Schedule Mastodon posts, polls, and content warnings on any instance from Claude or ChatGPT.

This is the posterly MCP server, used for Mastodon. The same connection works from Claude, ChatGPT, Cursor, and other MCP clients. It is not a separate Mastodon-only download.

Get Starter + API · $10/moHow to connect the MCP server

What you can do on Mastodon

Mastodon is decentralized, so connecting starts with the domain of your instance, such as mastodon.social, and you approve access there. No developer keys are involved, and any Mastodon instance works.

Your AI client can publish text, images or a video, and polls with 2 to 4 options. Choose public, unlisted, or followers only visibility, add a content warning that hides the post behind a click and marks media sensitive, set the post language, and quote another post on instances that support it. Alt text is supported on media.

Limits belong to the instance, not to posterly. Character count, attachment count, and whether a poll can be combined with media depend on the server you connect, so a post that works on one instance may need trimming on another. Every instance also has its own culture, so ask Claude to match the tone of your community and respect local rules on content warnings. Ask the assistant to run validate_post on your draft before scheduling, because that is where the limits of your instance are checked. The MCP server does not read Mastodon analytics.

  • Text posts
  • Images
  • Video
  • Multi-image
  • Polls
  • Audience controls
  • Visibility

Post types: text, image, video, carousel. Analytics are not read for this platform.

Tools

These are the tools your AI client uses for Mastodon. Ask it to call list_platforms with view=schema and the account_id before it sets anything specific to Mastodon.

Account and connection

  • whoamiWho am I

  • list_accountsConnected accounts

  • list_platformsPlatforms

  • create_connect_sessionStart a connect session

Posts

  • validate_postValidate a post

  • create_postCreate a post

    Show the caption, account, and time, then wait for confirmation before confirm=true.

  • create_posts_batchCreate posts in bulk

    1 to 25 posts in one confirmed request.

  • update_postEdit a post

    Show the caption, account, and time, then wait for confirmation before confirm=true.

  • list_postsPosts

  • get_postOne post

  • delete_postDelete posts

    Live removal needs an eligible connection and confirm_published. A refusal keeps the posterly record.

  • find_available_slotFind a free slot

  • generate_captionsGenerate captions

Media

  • upload_mediaUpload media

    Hosted requests are about 4MB, so this path is for small files. Large files use create_signed_upload or create_media_drop.

  • create_signed_uploadSigned upload link

  • create_media_dropMedia drop link

  • list_mediaMedia library

How to connect

  1. Add the hosted server in Claude, ChatGPT, Cursor, or another MCP client. Server URL: https://www.poster.ly/api/mcp. Sign in with posterly OAuth and press Allow. Use the www host. In ChatGPT, write actions need a Business, Enterprise, or Edu plan.
  2. Or, in a client that can run a local process (Cursor, Claude Code, Windsurf, and similar), use npx -y posterly-mcp-server@latest with a POSTERLY_API_KEY placeholder in that client's MCP config.
  3. Call whoami and list_accounts so you know which workspace the client is using.
  4. Connect Mastodon with the method below, then call list_platforms with view=schema and the account_id.

Mastodon

Start in the posterly dashboard and finish in your browser.

  • The dashboard asks for the instance domain, then redirects to that instance to authorize.
  • Apps are registered dynamically per instance, so no developer credentials are involved.
  • Instance domain (required): Mastodon instance domain, for example mastodon.social.
Connect Mastodon in the dashboard

Example prompts

  • Post this on Mastodon tomorrow at noon as unlisted with the content warning "long post" and alt text on the image.
  • Schedule a Mastodon poll with three options that closes after a day.
  • Run validate_post on this Mastodon draft for my instance, then trim it if anything is over the limit.

Mastodon limits

Platform rule
Status length and attachment count depend on the Mastodon instance you connect.

Request rates depend on your plan. The posterly MCP page lists them.

Pricing

API and MCP access is an add-on to any posterly plan. Starter plus API is $10 a month, charged now with no free trial on this checkout.

Get Starter + API · $10/moSee every plan

FAQ

What is the Mastodon MCP server?

It is the posterly MCP server, not a separate product. Connect it once and the same connection covers Mastodon and 17 other platforms, from Claude, ChatGPT, Cursor, and other MCP clients.

How do I connect Mastodon?

Add the hosted server at https://www.poster.ly/api/mcp and sign in with posterly, or run npx -y posterly-mcp-server@latest in a client that can start a local process. Mastodon: Start in the posterly dashboard and finish in your browser.

Which Mastodon servers work with the MCP server?

Any instance. Enter the instance domain, for example mastodon.social, and approve access on that instance. posterly registers with each instance itself, so you never handle developer credentials.

Can Claude set a content warning or followers-only visibility?

Yes. Visibility can be public, unlisted, or followers only, and spoiler text acts as a content warning that also marks attached media as sensitive.

Keep reading

MCP

posterly MCP server

Hosted OAuth setup, the local npm package, and the full tool list.

Scheduler

Mastodon scheduler

Schedule Mastodon from the posterly calendar and composer.

Guide

Mastodon guide

Read the long Mastodon guide, then come back to connect it.

Pricing

posterly pricing

Compare plans, then add API and MCP at checkout.

Other platform MCP servers