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MCP (streamable HTTP) · Mastodon

A Cursor Mastodon bot that asks first

If your project's community lives on Mastodon, a post about a fix is often more valued than a launch announcement. Cursor can write it from the change itself. Its agent reads the diff, drafts a toot through SocialHandoff's MCP tools, and follows fediverse habits: a clear first line, credit to the reporter, and hashtags at the end, not sprinkled through the text. The draft sits in the approval inbox; you publish it, not the agent.

Prompt

I fixed the timezone bug from issue #812 in lib/schedule.py. Write a Mastodon post for our project account explaining what was wrong in one sentence, who is affected, credit the reporter @ines@mastodon.social, and link the release. End with #Python. Under 450 characters.

How to do it

  1. Mint a Mastodon agent key In https://app.socialhandoff.com, open Connections, connect your Mastodon account, then create an agent key scoped to Mastodon with draft permission only. Copy the key when it is shown; only its hash is stored.
  2. Add the server to mcp.json In .cursor/mcp.json, add a server with url https://app.socialhandoff.com/mcp and a headers block carrying Authorization: Bearer and the Mastodon key. Keep the key in an environment variable, not in git.
  3. Confirm it in settings Open Cursor settings, then MCP, and check the server shows a green status with draft_post and schedule_post listed.
  4. Draft from the editor In agent chat, ask Cursor to turn the feature you just finished into a Mastodon post. It drafts, you approve in the inbox.

Example draft

Fixed in cronkit 3.2.1: jobs scheduled across a daylight saving change could run an hour early. It affected anyone using a non-UTC timezone with jobs between 1am and 3am local time.

Thanks to @ines@mastodon.social for the careful report in #812, which included a failing test.

Upgrade: pip install -U cronkit

#Python

Gotchas

  • Read your instance rules on automated posting. Many ask that bot-driven accounts tick the automated account box in profile settings.
  • Use CamelCase hashtags such as #OpenSource so screen readers say them correctly, and a content warning for long logs or spoilers.
  • 500 characters is only the default. Many instances allow more or less, so set the per-network length guardrail to your server's real limit.
  • Cursor reads .cursor/mcp.json from the project. If you commit that file, reference the key through an environment variable so it never lands in git.
Mastodon
  • Character limit: 500 characters on a default Mastodon server. Each instance can raise it, so check yours.
  • Links: Every URL counts as 23 characters, however long it is.
  • Media per post: Up to 4 attachments on a default server.
  • File sizes: Images up to 16 MB and video up to about 99 MB on a default install. Instances can set their own limits.
Mastodon scheduler with approval for any instance

Frequently asked questions

Can Cursor post to Mastodon without me leaving the editor?
It can draft and schedule without you leaving. Approval happens in the inbox, which you can keep open in a browser tab or on your phone.
Does Cursor know my instance's character limit?
Not by itself. Tell it in the prompt or brand memory, and set the per-network length guardrail so drafts over your limit are flagged.
Which Mastodon instances work?
Any Mastodon server. You enter your instance URL, sign in through that server's OAuth screen, and choose the account the agent drafts for.

Let your agents post. Keep the final say.

Connect your first agent in minutes. Every draft waits in your inbox until you approve it.

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