CostGate

Gate your MCP. Cut your bill.

CostGate reduces AI token consumption by optimizing MCP tool definitions and responses. Cursor-first, compatible with Claude Desktop and other MCP clients.

Repository layout (monorepo)

costgate/
├── packages/
│   ├── schema/     @costgate/schema   — shared log schema
│   ├── probe/      @costgate/probe    — measurement MCP (npm)
│   └── gate/       costgate-gate      — gateway MCP (Go binary)
├── docs/
├── examples/
└── scripts/

See docs/structure.md for why Probe and Gate share one repo.

Packages

Package	Dist	Description
@costgate/probe	npm	Measurement MCP — baseline token usage, call stats, JSONL logs
costgate-gate	binary	Gateway MCP — filtered tool exposure, delegation, cost reduction
@costgate/schema	workspace	Shared JSON Schema for logs

Quick start (Probe)

npm install
npm run build:probe

Add to Cursor ~/.cursor/mcp.json:

{
  "mcpServers": {
    "costgate-probe": {
      "command": "node",
      "args": ["/path/to/costgate/packages/probe/dist/index.js"],
      "env": {
        "COSTGATE_PROBE_LOG_DIR": "~/.costgate/logs"
      }
    }
  }
}

Or after npm publish: npx @costgate/probe

See examples/cursor/ for full configuration.

Quick start (Gate)

Requires Go 1.25+.

npm run build:gate
npm run test:gate   # smoke test (GitHub backend via ~/.costgate/backends.json)

Add to Cursor ~/.cursor/mcp.json (keep serena direct; see mcp-gate-github.json):

{
  "mcpServers": {
    "costgate-gate": {
      "command": "/path/to/costgate/packages/gate/bin/costgate-gate",
      "env": {
        "COSTGATE_CONFIG": "~/.costgate/backends.json"
      }
    }
  }
}

Filter mode (default): Tier A/B/C + discover_tools / invoke_tool. Set COSTGATE_GATE_MODE=transparent for pass-through baseline. See packages/gate/README.md.

Compare reduction: npm run compare (Before/After tools/list token estimate).

Session breakdown: npm run session-report (fixed + variable + overall % scenarios).

Production Cursor setup: npm run cursor:production — see examples/cursor/README.md.

Cloud metrics (opt-in): npm run cloud:upload — see costgate-cloud.

Plans (roadmap)

Plan	Scope
Free (OSS)	Probe + Gate core
Pro	Automated cloud reports (costgate-cloud)
Team / Enterprise	Team dashboard, policies, custom proposals, support

Documentation

• Development roadmap
• Repository structure
• Docker / Dev Container
• Architecture
• Log schema
• Contributing

License

MIT — see LICENSE