Overview - Invoice-AI API

The Invoice-AI MCP server lets an AI assistant work in your account. It can look up customers and invoices, draft invoices, and, if you allow it, finalize, email, mark paid or void them. Each of those last four asks you to confirm in the chat first.

https://invoice.horizonpay.co/mcp

Connect

Claude
ChatGPT
Claude Code
Cursor
Other

claude.ai and Claude Desktop share connectors.

Open Customize → Connectors. On some versions it’s under Settings → Connectors.
Choose Add custom connector and name it Invoice-AI.
Paste https://invoice.horizonpay.co/mcp as the server URL.
Add it, then choose Connect. Claude opens Invoice-AI so you can approve it.

On a Team or Enterprise plan, an owner adds the connector once in the organization’s connector settings. Each person then connects their own account.

In Settings, open Apps & Connectors → Advanced settings and turn on Developer mode.
Back in Apps & Connectors, choose Create and name it Invoice-AI.
Enter https://invoice.horizonpay.co/mcp as the MCP server URL and choose OAuth for authentication.
Create it. ChatGPT opens Invoice-AI so you can sign in and approve it.

Menu names and Developer mode availability may differ by ChatGPT plan.

claude mcp add --transport http invoice-ai https://invoice.horizonpay.co/mcp

Then run /mcp in Claude Code and pick invoice-ai to sign in. Your browser opens so you can approve it.To skip the sign-in, pass an API key instead:

claude mcp add --transport http invoice-ai https://invoice.horizonpay.co/mcp \
  --header "Authorization: Bearer inv_live_..."

Add this to ~/.cursor/mcp.json, or to .cursor/mcp.json in one project:

{
  "mcpServers": {
    "invoice-ai": {
      "url": "https://invoice.horizonpay.co/mcp"
    }
  }
}

Connect it from Cursor’s MCP settings. Cursor opens Invoice-AI so you can approve it.To use an API key instead, add a header:

{
  "mcpServers": {
    "invoice-ai": {
      "url": "https://invoice.horizonpay.co/mcp",
      "headers": { "Authorization": "Bearer inv_live_..." }
    }
  }
}

Any client that supports remote MCP servers over Streamable HTTP can connect to https://invoice.horizonpay.co/mcp.

If it supports MCP OAuth, it finds the sign-in page on its own. See Authentication.
If it doesn’t, create an API key with the AI assistant preset and send it as Authorization: Bearer inv_live_....

The same steps are in the app, in Settings → AI assistants.

Approve access

When you connect over OAuth, Invoice-AI shows a consent screen. It names the app, shows whether its domain is verified, and lists permissions in three groups:

Group	Pre-ticked
Look things up	Yes
Create customers and draft invoices	Yes
Finalize, email, and record payments	No. Tick these only if you want the assistant to do them.

Untick anything you don’t want, then choose Approve. You can disconnect the app at any time in Settings → AI assistants.

Try it

“Which invoices are overdue, and how much is owed in total?”
“Invoice Acme Ltd $1,500 for the October design retainer, due in 14 days.”
“Email that invoice to Acme.”
“Acme paid INV-0041 by bank transfer yesterday. Mark it paid.”

For the last two, the assistant shows you a preview and waits for your yes. See Confirmations.

How it works

Transport: Streamable HTTP, stateless. Each request stands alone, so there’s no session to keep alive.
Same rules as the API: every tool runs the same operation as a REST endpoint, with the same validation, scopes and rate limits. See Tools.
Audited: every tool call appears in Settings → Activity as MCP <tool>, for example MCP send_invoice, with the app that made it.

​Connect

​Approve access

​Try it

​How it works

Connect

Approve access

Try it

How it works