MCP Fax Server for AI Assistants
Send FAX Mail ships a hosted Model Context Protocol server at /mcp so an AI assistant can send a fax, look one up, and read your numbers as tool calls. It speaks JSON-RPC 2.0 over the Streamable HTTP transport and authenticates with the same bearer API key as the REST API, so there is no separate credential to manage. An assistant that supports remote MCP connects to the endpoint, lists the available tools, and calls send_fax, list_faxes, get_fax, or list_numbers on your behalf. Every tool runs through the same send pipeline as the dashboard, so quota, HIPAA, and number gates all still apply.
Plan requirement
The MCP server is part of the Business ($79.99/mo) and Enterprise ($169.99/mo) plans, the same gate as the REST API. A key on a lower plan is refused at the endpoint with a 403 plan_upgrade_required, so it never half-works. Each tool is also limited by the scopes on the key you connect with.
How it works
The endpoint is POST /mcp, and it implements the standard MCP methods: initialize, ping, tools/list, and tools/call. You authenticate exactly like the REST API — an Authorization: Bearer header carrying a key that begins sfm_live_ — so the same key gates both. When the assistant calls tools/list it gets four tools back: send_fax routes into the shared gated send pipeline, list_faxes and get_fax read history, and list_numbers reads your provisioned numbers. Each tool is scope-checked against the key, so a send-only key cannot list history. Tool-level problems come back as isError results the model can read and react to, while malformed protocol calls return proper JSON-RPC error envelopes. Notifications are acknowledged with a 202.
What you can do
- ✓Let an AI assistant send a fax with the send_fax tool, gated by the same quota and HIPAA rules as the dashboard
- ✓Read recent faxes with list_faxes and inspect one with get_fax
- ✓Read the account's provisioned numbers with list_numbers
- ✓Authenticate with the same bearer API key as the REST API — no second credential
- ✓Scope each tool to the key, so a send-only key cannot read history
- ✓Connect Claude Desktop through the bundled stdio bridge that forwards to /mcp
Setup steps
- 1Confirm the account is on Business or Enterprise, since the MCP endpoint shares the API plan gate
- 2Create an API key at /dashboard/developers with the scopes the assistant needs
- 3Point your MCP-capable assistant at the /mcp endpoint and add an Authorization: Bearer header
- 4Have the assistant call initialize, then tools/list to discover send_fax, list_faxes, get_fax, and list_numbers
- 5For Claude Desktop, install the stdio bridge and set SENDFAXMAIL_API_KEY (the config is shown at /dashboard/developers)
- 6Call send_fax with a recipient and a document, then read the returned fax id back with get_fax
Example
POST /mcp
Authorization: Bearer sfm_live_xxxxxxxx
Content-Type: application/json
{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/call",
"params": {
"name": "send_fax",
"arguments": { "to": "+15551234567", "document_url": "https://example.com/invoice.pdf" }
}
}MCP Fax Server — FAQ
It is a hosted Model Context Protocol endpoint at /mcp that exposes faxing as tools an AI assistant can call, rather than raw HTTP routes you script by hand. Under the hood it uses the same send pipeline and the same bearer key as the REST API, so the gates are identical; the difference is that the assistant discovers and calls the tools itself over JSON-RPC.
Four: send_fax to send through the gated pipeline, list_faxes to read recent faxes, get_fax to inspect a single fax by id, and list_numbers to read the numbers on the account. Each one is scope-checked against your key, so a key without faxes:read cannot call list_faxes even though the tool is advertised.
Claude Desktop talks to local MCP servers over stdio, so we ship a small stdio bridge package that forwards stdio JSON-RPC to the hosted /mcp endpoint. You set SENDFAXMAIL_API_KEY (and optionally the endpoint URL) in the Claude Desktop config; the exact snippet is shown at /dashboard/developers. Nothing about the account changes — the bridge just relays the same authenticated calls.
No. send_fax routes through the same shared pipeline as the dashboard and REST API, so the monthly page quota, the HIPAA no-attach rules, and the provisioned-number requirement all still apply. A tool call that would exceed quota or violate a gate comes back as an isError result the model can read, not a silent send.
Build with the MCP Fax Server
API access and webhooks are included on the Business and Enterprise plans. Create a key at /dashboard/developers and start sending.
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