mcp-pay

Payment awareness layer for MCP (Model Context Protocol)

[](LICENSE)

mcp-pay extends the MCP ecosystem with payment capabilities. It provides:

• Schema: A JSON manifest (mcp-pay.json) for declaring pricing and payment rails
• Reference Server: A Rust implementation demonstrating payment-gated MCP tools
• Protocol: HTTP 402 payment flow compatible with x402, MPP, Lightning, and card payments

| Ecosystem | Discovery | Payment | |-----------|-----------|---------| | MCP Registry | Tools, resources, prompts | None | | x402 Bazaar | After payment | x402 only | | Tempo MPP | In-network | MPP only | | mcp-pay | At .well-known | All rails |

mcp-pay bridges these ecosystems by providing a rail-agnostic payment manifest that works with all payment protocols.

# Clone and build
git clone https://github.com/neul-labs/mcp-pay
cd mcp-pay
cargo build --release

# Configure (optional)
export PAY_TO_ADDRESS=0x1234567890abcdef1234567890abcdef12345678
export HTTP_ADDR=127.0.0.1:3000

# Run
cargo run -p mcp-pay-server

# Get payment manifest
curl http://localhost:3000/.well-known/mcp/pay.json | jq

# Get weather (FREE)
curl "http://localhost:3000/api/weather?city=London" | jq

# Get forecast (PAID - returns 402)
curl -i "http://localhost:3000/api/forecast?city=Tokyo"
# HTTP/1.1 402 Payment Required
# X-PAYMENT-REQUIRED: eyJ4NDAyX3ZlcnNpb24i...

mcp-pay/
├── crates/
│   ├── mcp-pay-schema/     # Schema types + validation
│   ├── mcp-pay-server/     # Reference implementation
│   └── mcp-pay-cli/        # Registry queries (Phase 2)
├── specs/
│   ├── schema/
│   │   └── mcp-pay.schema.json
│   └── mcp-pay-specification.md
└── README.md

Serve at /.well-known/mcp/pay.json:

{
  "mcp_pay": "0.1",
  "server_card": "/.we