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satgate-proxy

0.3.0
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  • License MIT

Budget-enforced MCP proxy — hard-cap your AI agent tool spend

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    Readme

    satgate-proxy

    Budget-enforced MCP proxy — hard-cap your AI agent tool spend.

    MCP servers are an open tap. Every tools/call costs money and there's no built-in spending limit. satgate-proxy sits between your MCP client (Claude Desktop, Cursor) and the server, enforcing a hard budget cap.

    Zero dependencies. Node.js built-ins only. npx and go.

    Quick Start — Local Mode (New in v0.3.0)

    No server, no API key, no account. Budget enforced in-process:

    npx satgate-proxy --local --budget 5.00 \
  --server @modelcontextprotocol/server-google-search

    Or with a config file:

    # satgate.yaml
server: @modelcontextprotocol/server-google-search
budget: 5.00

mcp_pricing:
  web_search: 5
  dalle_generate: 50
  '*': 1
    npx satgate-proxy --local --config satgate.yaml

    Claude Desktop config (local mode):

    {
  "mcpServers": {
    "google-search": {
      "command": "npx",
      "args": [
        "satgate-proxy",
        "--local", "--budget", "5.00",
        "--server", "@modelcontextprotocol/server-google-search"
      ]
    }
  }
}

    No env vars needed. No accounts. Just a budget cap.

    SaaS Mode (Teams & Enterprise)

    For server-side enforcement with L402 macaroons:

    {
  "mcpServers": {
    "google-search": {
      "command": "npx",
      "args": [
        "satgate-proxy",
        "--cap", "5.00",
        "--server", "@modelcontextprotocol/server-google-search"
      ],
      "env": {
        "SATGATE_API_KEY": "your_macaroon_here"
      }
    }
  }
}

    Get your API key at cloud.satgate.io.

    How It Works

    Local Mode

    ┌──────────────┐     stdio      ┌────────────────┐     stdio      ┌──────────────┐
│ Claude       │ ──── JSON-RPC ──▶ satgate-proxy  │ ──── JSON-RPC ──▶ MCP Server  │
│ Desktop      │ ◀── JSON-RPC ── │ (budget gate)  │ ◀── JSON-RPC ── │ (child proc) │
│ / Cursor     │                 └────────────────┘                 └──────────────┘
└──────────────┘                  ↑ intercepts tools/call
                                  ↑ deducts from budget
                                  ↑ blocks when exhausted

    The proxy spawns your MCP server as a child process, intercepts every tools/call, deducts from your budget based on per-tool pricing, and blocks calls when the budget is exhausted.

    SaaS Mode

    ┌──────────────┐     stdio      ┌────────────────┐     SSE/HTTP     ┌──────────────┐
│ Claude       │ ──── JSON-RPC ──▶ satgate-proxy  │ ──── JSON-RPC ──▶ SatGate      │
│ Desktop      │ ◀── JSON-RPC ── │ (this package) │ ◀── JSON-RPC ── │ MCP Proxy    │
│ / Cursor     │                 └────────────────┘                  │ + Budget     │
└──────────────┘                                                     │ Enforcement  │
                                                                     └──────┬───────┘
                                                                            │
                                                                     ┌──────▼───────┐
                                                                     │ MCP Server   │
                                                                     │ (hosted)     │
                                                                     └──────────────┘

    Config File (satgate.yaml)

    Instead of CLI flags, you can use a config file:

    # satgate.yaml
server: @modelcontextprotocol/server-google-search
budget: 5.00

mcp_pricing:
  web_search: 5        # 5 cents per search
  dalle_generate: 50   # 50 cents per image
  '*': 1               # 1 cent default for unlisted tools

    Pricing is in cents. The '*' wildcard sets the default cost for any tool not explicitly listed.

    CLI Flags

    Flag Description Default
    --server <package> MCP server package to proxy (required) —
    --local Run in local mode (no SatGate server needed) off
    --budget <amount> Budget cap in USD (local mode) unlimited
    --config <path> Path to satgate.yaml config file —
    --cap <amount> Budget cap in USD (SaaS mode) —
    --endpoint <url> SatGate proxy endpoint https://satgate-mcp-saas.fly.dev
    --key <macaroon> API key (or SATGATE_API_KEY env var) —
    --verbose Debug logging to stderr off
    -h, --help Show help —

    Why?

    MCP gives AI agents direct access to paid APIs — search, code execution, databases, you name it. There's no built-in spending limit. A runaway agent can burn through hundreds of dollars in minutes.

    satgate-proxy adds a hard cap:

    • Local mode: Set --budget 5.00 → agent can spend at most $5, enforced in-process
    • SaaS mode: Set --cap 5.00 → enforced server-side with L402 macaroons
    • Zero dependencies — npx runs it instantly

    Zero Dependencies

    This package uses only Node.js built-ins (child_process, http, https, fs). No node_modules, no install step. npx satgate-proxy just works.

    License

    MIT