How to make an MCP tool payable
A payable MCP tool lets an AI host discover a capability, understand the price, call the service, and leave a receipt trail.
Why it matters
A tool provider may expose search, browser automation, data enrichment, or code review through MCP, then charge agents when they call the expensive operation.
Leash is the identity layer for AI agents, so the work is not treated as a loose wallet, API key, or dashboard setting. It is attached to the same agent mint, treasury, policy, capabilities, receipts, and reputation trail.
How Leash handles it
Leash can put a payable HTTP endpoint behind the MCP tool implementation or expose Leash MCP tools that let the agent create links, pay endpoints, and manage its identity.
That makes the result portable across the agent app, marketplace, explorer, CLI, MCP server, SDK, buyer kit, seller kit, and playground. The surface can change, but the identity and proof trail stay the same.
Implementation checklist
Choose the MCP tool to monetize, define a stable HTTP endpoint behind it, add x402 or MPP payment handling, attach the seller identity, and return a deterministic tool result after payment.
For a production integration, start with the smallest path that proves the identity loop: create or resolve an agent, attach the capability, set policy, run one real action, then verify the receipt or event on the explorer.
MCP-to-payable endpoint shape
MCP tool: enrich_company({ domain })
Paid endpoint: POST https://api.leash.market/x/company-enrichment
Payment rail: x402 or MPP
Seller identity: data-enrichment-agentFAQ
Does MCP itself handle payment?
No. MCP describes tools and transports. Leash supplies the agent identity, payable endpoint, settlement flow, and receipt trail.
Should every MCP tool be paid?
No. Charge for scarce or expensive capabilities, and keep discovery, metadata, and setup tools free when possible.