Developers & agents

Name: Fax Monster
Brand: Fax Monster
Price: 1.99 USD

Fax Monster exposes the fax engine via REST API and remote MCP (CLI coming soon). A human owner signs in with Google or a passwordless email magic link, tops up prepaid credits, and issues API keys for agents. AI agents cannot create accounts or keys — only the verified owner can.

Prepaid credits

Shared-number send: $1.99 per fax (debited when you send). Private number rental: $4.99 per 30 days; sends on that number use the rental's page allowance (no per-fax debit).

Failed faxes do not use your page allowance or prepaid API credits. Fax only ($1.99): one free retry, then email us for a refund if it still fails.

With an active Fax Monster Business subscription, API and MCP sends use your Business monthly page bucket (1,000 pages in + out combined). They do not spend prepaid API credits unless you send from the shared number without Business or rent a separate API private number.

REST API

Base URL: https://fax.monster/api/v1
OpenAPI: /api/v1/openapi.json
Auth header: Authorization: Bearer fm_live_…

MCP (Streamable HTTP)

Cursor and other clients that accept a URL:

{
  "mcpServers": {
    "fax-monster": {
      "url": "https://fax.monster/mcp",
      "headers": {
        "Authorization": "Bearer fm_live_YOUR_KEY"
      }
    }
  }
}

Claude Desktop only starts local programs, so connect it through the free mcp-remote helper (needs Node.js):

{
  "mcpServers": {
    "fax-monster": {
      "command": "npx",
      "args": [
        "mcp-remote", "https://fax.monster/mcp",
        "--header", "Authorization: Bearer fm_live_YOUR_KEY"
      ]
    }
  }
}

More clients (Claude Code and others): MCP server setup.

CLI

npm package coming soon. Today you can use the REST API or MCP from any agent runtime.

Agent docs

/llms.txt — concise machine-oriented overview for LLM agents.