@leashmarket/mcp-core

Host-agnostic core for every Leash MCP surface.

Defines the LeashHost runtime contract, LeashTool primitive, and the full LEASH_TOOLS catalogue that all adapters (@leashmarket/mcp, Claude Agent SDK, browser runtimes) iterate over.

Install

npm install @leashmarket/mcp-core
# or
pnpm add @leashmarket/mcp-core

What lives here

| Export | Purpose | | -------------------------- | ------------------------------------------------------------------------------------------------------ | | LeashHost | Runtime contract every host implements (wallet, RPC, API key, …) | | LeashTool / defineTool | Tool-definition primitive (name, Zod schema, typed handler) | | LEASH_TOOLS | Canonical tool list adapters iterate — discover, pay, agent API keys, receipts, spend limits, etc. | | helpers/* | Pure utilities: probePaymentLink, fetchDiscover, fetchReputation, token catalog, address helpers |

Payment-link tool contract

leash_create_payment_link is the shared tool definition used by @leashmarket/mcp, @leashmarket/cli, and in-product agent hosts. It supports:

• method: "GET" | "POST" — how buyers call the hosted paywall.
• protocol: "x402" | "mpp" — which payment rail the hosted paywall speaks.
• upstream_url — an existing API endpoint to call after settlement.
• expected_request_body — arbitrary JSON metadata describing the POST body buyers should send.

expected_request_body is not the live request body. The buyer supplies the real body later through leash_pay_payment_link or another x402/MPP client, and the hosted paywall forwards it to upstream_url only after payment settles. leash_pay_payment_link mirrors the same contract with method and raw body arguments for POST calls.

Agent API-key tools

leash_create_agent_api_key, leash_list_agent_api_keys, and leash_revoke_agent_api_key let a configured agent create and manage its own Leash API key. These calls are authenticated with X-Leash-Sig, so no existing LEASH_API_KEY is required to bootstrap one. Created keys are bound to the active agent mint, owned by the executive public key, and scoped as exactly agent; plaintext is returned once on create.

Usage

import { LEASH_TOOLS, type LeashHost } from '@leashmarket/mcp-core';

// Implement the host contract for your runtime
const host: LeashHost = {
  apiKey: process.env.LEASH_API_KEY!,
  apiUrl: 'https://api.leash.market',
  network: 'solana-mainnet',
  rpcUrl: 'https://api.mainnet-beta.solana.com',
  signer: mySigner,
};

// Iterate tools and wire them into your adapter
for (const tool of LEASH_TOOLS) {
  registerTool(tool.name, tool.schema, (args) => tool.handler(host, args));
}

Using helpers directly

import { probePaymentLink, fetchDiscover } from '@leashmarket/mcp-core/helpers';

// Check if a URL is a valid x402/MPP paywall
const result = await probePaymentLink('https://api.example.com/endpoint');

// Browse the discover catalog
const { items } = await fetchDiscover('https://api.leash.market', {
  capability: 'translate text',
});

Docs

Full tool reference and host contract: docs.leash.market/sdk/mcp-core

Develop

pnpm --filter @leashmarket/mcp-core build
pnpm --filter @leashmarket/mcp-core test