Post to X from n8n

What n8n can do with calmposts

n8n starts workflows on a schedule, a webhook, a new item in an RSS feed or a row in a sheet. With calmposts behind an AI Agent node, a workflow turns each new item into an n8n Twitter (X) post, or a thread, and puts it in calmposts' queue, where it waits for your approval.

There are two ways in. The MCP Client Tool gives an AI Agent node calmposts' tools, and the model chooses them; the MCP Client node calls one tool as an ordinary step, with arguments mapped from earlier nodes and no model involved. Both take the key from an n8n credential, stored once and reused by every workflow.

calmposts' X (Twitter) MCP server gives n8n 11 tools, the same set every client gets:

Set up calmposts in n8n

Check the key before you start

Create a key in calmposts under API & MCP (it's shown only once), then ask the server for its tools. A list of 11 tools means the address and the key are right; a 401 means the key is wrong or was sent without “Bearer ”.

curl -s https://calmposts.com/mcp \
  -H "Authorization: Bearer cp_live_…" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'
# 200 {"jsonrpc":"2.0","id":1,"result":{"tools":[…]}}

Setup 1: An AI Agent with the MCP Client Tool

The agent reads the item, writes the post and picks the tool.

1. Create a key in calmposts under API & MCP. In n8n, create a Bearer Auth credential and paste the key as its Bearer Token, without “Bearer ”: n8n adds it.

2. In your workflow, open the AI Agent node's tools and add MCP Client Tool.

3. Fill it in:

   Endpoint:          https://calmposts.com/mcp
   Server Transport:  HTTP Streamable
   Authentication:    Bearer Auth
   Bearer Token:      cp_live_…
   Tools to Include:  All

4. Say in the agent's prompt what to do, for example “Write one X post about this article and save it in calmposts with when=queue”, run the workflow once and read the node's output.

Setup 2: A fixed step with the MCP Client node

No model: every run calls create_post with the fields you map.

1. Add an MCP Client node after your trigger and fill it in:

   MCP Endpoint URL:  https://calmposts.com/mcp
   Server Transport:  HTTP Streamable
   Authentication:    Bearer Auth
   Tool:              create_post
   Input Mode:        JSON

2. Pass the arguments as JSON, with fields from earlier nodes. ACCOUNT_ID comes from list_accounts: run that tool once in another MCP Client node to read it.

   {
     "text": "{{ $json.title }} {{ $json.link }}",
     "account_ids": ["ACCOUNT_ID"],
     "when": "queue"
   }

Signing in: a key or OAuth

The Bearer Auth credential sends Authorization: Bearer with your key on every request, which is what calmposts expects. A key does not expire, so it suits workflows that run at night.

If you pick Header Auth instead, set the name to Authorization and the value to Bearer cp_live_…, with the space.

n8n also has an MCP OAuth2 credential that registers itself (Dynamic Client Registration is on by default). calmposts accepts its redirect URL when your n8n is served over https or from localhost; for a workflow that runs unattended, a key is simpler.

Create a separate key for n8n with only the permissions it needs (accounts:read, posts:read, posts:write), so you can revoke it without touching your other agents.

Check that it works

• In an MCP Client node, the Tool list fills with calmposts' 11 tools: the endpoint and the key work.
• Run the AI Agent with a test item: its log shows calls to list_accounts and create_post.
• The new post is under Posts in calmposts, as a draft or in the queue, with the source mcp.

Prompts to try

Ask in your own words and the agent picks the tools. A few that work well:

• “For each new RSS item, write one X post under 280 characters with the link and save it in calmposts with when=queue for my X account.”
• “Turn this release note into a short thread for X and Bluesky and save it as a draft.”
• “Call get_limits first; if fewer than 3 posts are left today, save the post as a draft instead of queueing it.”
• “Never use when=now. If calmposts answers duplicate_recent, rewrite the post once and try again.”

Networks, threads and approval

Posts go to X and Bluesky. A thread goes out as a reply chain on X and Bluesky. Coming soon: Threads and LinkedIn.

Write once, post everywhere: your agent sends one text for every account it picks. If the text is longer than a network allows, calmposts posts it there as a thread, splitting at a paragraph break, then at the end of a sentence, then at a space, with nothing numbered or added. calmposts checks each network's rules and your plan's limits before it saves the post and names the field that's wrong, so the agent can fix the text and try again.

By default your agent's posts wait for you. They come back as pending_approval, and you approve or reject each one in the app, in Telegram or from the email calmposts sends. The workspace owner can let agents publish on their own, but only when both the workspace and the API key are set to publish. X expects an account that posts automatically to carry its Automated label (Settings → Your account → Account information → Automation).

Which networks work today→

Limits and costs

• Agents need a paid plan: the Free plan has no API keys and can't approve connected apps. API keys per plan: Pro 3 · Advanced 10 · Agency 25.
• Your agent's posts count the same as yours. Posts a day: Pro 20 · Advanced 100 · Agency 300. Posts with a link per month: Pro 30 · Advanced 300 · Agency 600. Each post in a thread counts.
• Posts with a link are counted separately because X charges every app $0.015 per post and $0.20 per post with a link. Your plan includes X's fees, so you don't need an X developer account or an X API bill of your own.
• Try it first: 7-day free trial. Card required. 5 posts with a link during the trial.
• Each key can make 60 requests a minute across MCP and REST; beyond that, the server returns 429 with Retry-After.

Pricing→

What to know about n8n

• n8n's docs page for the MCP Client Tool still calls the field SSE Endpoint, which belongs to the node's first version. Current versions have Endpoint and a Server Transport choice: pick HTTP Streamable. calmposts has no SSE endpoint.
• An RSS workflow puts a link in every post, and posts with a link have their own monthly number on each plan, because X charges more for them. Check that number before you switch the workflow on.
• The nodes' Timeout option is 60 seconds by default, far more than calmposts needs; a create_post with images takes longest, while calmposts downloads them.
• A workflow that posts for several clients can pass customer_id to list_accounts and list_posts to stay within one client's channels.

Without MCP: the REST API

Everything the tools do is also a REST call under /api/v1 with the same key, which suits a script or a workflow step that only speaks HTTP. calmposts posts through its own approved X app, so you don't need X API keys of your own.

export CALMPOSTS_API_KEY=cp_live_…
curl -H "Authorization: Bearer $CALMPOSTS_API_KEY" https://calmposts.com/api/v1/accounts
curl -X POST https://calmposts.com/api/v1/posts \
  -H "Authorization: Bearer $CALMPOSTS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"parts":[{"text":"Calm posts, scheduled."}],"targets":[{"account_id":"ACCOUNT_ID"}],"schedule":{"mode":"queue"}}'

REST API docs→

The n8n docs this page follows

• n8n docs: MCP Client Tool node
• n8n docs: MCP Client node
• n8n docs: MCP credentials
• n8n docs: HTTP Request credentials (bearer auth)
• n8n source: the MCP Client Tool node

calmposts is an independent service and is not affiliated with or endorsed by the makers of n8n. Product names belong to their owners.