Post to Facebook from n8n with an AI agent

Can n8n post to Facebook Pages?

Postgale is the secure layer for AI agents on social media. MCP (Model Context Protocol) is the open standard that lets AI assistants such as Claude and Cursor use outside tools. An MCP server is what they connect to. n8n does not reach Facebook on its own; with Postgale connected it gets tools for the Facebook accounts you connected and nothing else.

What do you need?

• A Facebook Page you administer. Personal profiles cannot be connected.
• A Postgale workspace; the admin signs in with Facebook and chooses which Pages to connect.
• For photos, video, Reels and Stories: media on a public HTTPS URL (upload it with upload_media or bring your own).
• n8n, set up as below (Workflows with the HTTP Request or MCP Client Tool node).

Step 1: connect your Facebook Pages account

1. Create a Postgale workspace and open Dashboard → Accounts.
2. Choose Connect Facebook Pages and sign in with the account you own, on the platform’s own page. Postgale stores the tokens encrypted and refreshes them.

Step 2: connect n8n to Postgale

How do I set up the MCP Client Tool node?

1. In Postgale, open Dashboard → API keys, create a key and copy it (it starts with sk_ and is shown once). Connect the social accounts the agent may use under Dashboard → Accounts.
2. Add an AI Agent node with your model, and attach an MCP Client Tool node to it.
3. In the MCP Client Tool node set the endpoint to https://postgale.com/mcp, the transport to HTTP streamable, and authentication to a Bearer or Header Auth credential carrying Authorization: Bearer sk_….
4. Leave the tool list on “all” to start, or select only the read-only tools until you trust the workflow.
5. Give the agent a system prompt that states the account ids it may use and whether it must save drafts or may schedule.

Ask your agent“You manage the Northline accounts in Postgale (ids in the context). For each new blog post in the input, draft one Instagram caption with the cover image and one Threads post, save them as drafts, and reply with the Postgale post ids.”

How do I set up the HTTP Request node?

1. In Postgale, open Dashboard → API keys, create a key and copy it (it starts with sk_ and is shown once). Connect the social accounts the agent may use under Dashboard → Accounts.
2. In n8n create a credential of type Header Auth with name Authorization and value Bearer sk_… (your key).
3. Add an HTTP Request node: method POST, URL https://postgale.com/api/v1/posts, authentication Header Auth with that credential, body type JSON:

{
  "content": "{{ $json.caption }}",
  "scheduledFor": "{{ $json.publishAt }}",
  "platforms": [
    {
      "accountId": "acc_instagram",
      "platformSpecificData": {
        "mediaUrl": "{{ $json.imageUrl }}"
      }
    },
    {
      "accountId": "acc_threads"
    }
  ]
}

1. Get the account ids once with a GET to https://postgale.com/api/v1/accounts using the same credential.
2. Optional: send an x-request-id header built from your trigger id, so a re-run of the workflow returns the same post instead of a duplicate.
3. To know when the post is live, add a Webhook node and register its URL in Postgale (Dashboard → Webhooks); Postgale sends post.published or post.failed, signed with HMAC-SHA256.

What can I ask the agent to do on Facebook?

Check the connection first: “Which Facebook accounts are connected in Postgale?” Then, in plain language:

Ask your agent“Share our new blog post on the Facebook Page with a two-line intro, scheduled for Monday at 10am.”

Ask your agent“Post this video as a Facebook Reel with the caption from the brief, as a draft.”

Ask your agent“Draft replies to today’s Messenger messages about delivery times.”

{
  "content": "The fall drop is live. Shipping Thursday. Read the story behind it:",
  "platforms": [
    {
      "accountId": "acc_facebook_page",
      "platformSpecificData": {
        "link": "https://example.com/blog/fall-drop"
      }
    }
  ],
  "publishNow": true
}

Which Facebook rules does Postgale enforce?

• One Postgale account per Page. After sign-in the admin picks Pages; an agent that started the connection completes the choice with select_connection.
• Post text up to 63,206 characters. Photo sets take 2 to 10 images.
• Reels and video Stories are uploaded by URL in Facebook’s two-phase flow; Postgale tracks processing and reports when the post is live.
• Messenger replies are allowed within 24 hours of the person’s last message (7 days with Meta’s human-agent tag); outside the window Postgale sends nothing and says why.
• Ads never spend by accident: boosts and campaigns are created paused and need an explicit confirmation to go live.

How do I keep a person in the loop?

• Approval: tick “Hold posts from this app for approval” when you sign in, or in the Postgale dashboard require approval for the API key the agent uses (or for the whole workspace, or one account). Posts then wait as pending approval; comment replies and moderation, direct messages, WhatsApp sends and edits to live posts wait in the same queue. A person approves, edits or rejects each one in Dashboard → Approvals; the agent’s own key or sign-in cannot approve.
• Tool annotations: every Postgale tool declares whether it only reads, writes, or publishes live, deletes or spends. Clients that honour annotations ask before destructive tools run.
• Audit log: every write the agent makes is recorded with the key or the connected app, the action and the time.
• Revoking: each sign-in appears under Dashboard → Connected apps and each key under Dashboard → API keys; either can be revoked at any time.

What can’t an agent do on Facebook through Postgale?

• Post to a personal profile or a group. Facebook’s API publishes to Pages.
• Message someone first on Messenger. Meta only allows replies to people who wrote to the Page.
• Spend on ads without a confirmation step.

Common questions