Answer WhatsApp from n8n with an AI agent

Can n8n answer customers and send messages on WhatsApp Business?

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 WhatsApp on its own; with Postgale connected it gets tools for the WhatsApp accounts you connected and nothing else.

What do you need?

• A WhatsApp Business Account and a phone number for it, set up through Meta’s Embedded Signup from the Postgale dashboard, or an existing number connected with its token.
• A Postgale workspace, and a sign-in or an API key for the agent.
• Message templates approved by Meta if the agent must write first or outside the 24-hour window.
• n8n, set up as below (Workflows with the HTTP Request or MCP Client Tool node).

Step 1: connect your WhatsApp Business account

1. Create a Postgale workspace and open Dashboard → Accounts.
2. Choose Connect WhatsApp Business and sign in with the account you own, on Meta’s own Embedded Signup 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 WhatsApp?

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

Ask your agent“Answer the new WhatsApp questions about opening hours. Hold every reply for my approval.”

Ask your agent“Send the “order ready” template to the customer in this conversation.”

Ask your agent“Summarise today’s WhatsApp conversations and list the ones still waiting for an answer.”

{
  "to": "+14155550132",
  "type": "text",
  "text": "Yes, M restocks Tuesday. Want me to hold one?"
}

Which WhatsApp rules does Postgale enforce?

• Free-form replies are allowed for 24 hours after the customer’s last message. Outside that window only approved templates can be sent; Postgale refuses anything else and explains why.
• WhatsApp has no human-agent extension of the window (Instagram and Messenger do); Postgale does not pretend otherwise.
• A number must be registered before it can send; a test number can only message its allowed recipients. Postgale returns the specific error code for each case.
• The business token from Embedded Signup is stored encrypted and never shown to the agent.

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 WhatsApp through Postgale?

• Send free-form messages outside the 24-hour window. Meta requires an approved template.
• Avoid Meta’s per-conversation charges. Meta bills the WhatsApp Business Account directly for template messages.
• Post to a feed. WhatsApp is messaging only.

Common questions