X402 Universal Payer MCP Server

X402 Universal Payer is an MCP integration. Pay any x402 endpoint on the open web: auto-paying bridge with Bazaar discovery and spend caps.

Packages and local setup

The published npm package is @three-ws/mcp-bridge, version 1.0.2. Its declared MCP transport is stdio.

The package declares MCP_BRIDGE_EVM_PRIVATE_KEY: 0x-prefixed 32-byte hex private key that funds USDC payments on EVM chains (Base, Arbitrum, …). At least one of the EVM/SVM keys is required. Treat like cash — use a dedicated low-balance wallet.; MCP_BRIDGE_SVM_PRIVATE_KEY: Solana secret key that funds USDC payments: base58 64-byte secret key (Phantom / solana-keygen format) or a JSON array of 64 integers. At least one of the EVM/SVM keys is required. Treat like cash.; MCP_BRIDGE_MAX_PRICE_PER_CALL_ATOMIC: Per-call spending cap in atomic units (USDC has 6 decimals). Payments above this abort with a clear reason.; MCP_BRIDGE_MAX_TOTAL_ATOMIC: Cumulative session spending ceiling in atomic units. Once total spend would exceed it, further payments abort until restart.; MCP_BRIDGE_ALLOWED_PAYTO: Comma-separated payee allowlist. When set, any payment whose payTo address is not listed is refused.; MCP_BRIDGE_ALLOWED_HOSTS: Comma-separated hostname allowlist for outbound paid requests. When set, any other host is refused before a request is signed.; MCP_BRIDGE_ALLOW_HTTP: Set to 1 to allow http:// targets (local development only). https is enforced otherwise.; MCP_BRIDGE_DISCOVER_LIMIT: Max number of x402 Bazaar resources to register as dynamic tools at startup. Set 0 to disable discovery.; MCP_BRIDGE_BAZAAR_URL: x402 Bazaar discovery endpoint. Override to point at a self-hosted or alternative bazaar.; MCP_BRIDGE_BATCH_DEPOSIT_MULTIPLIER: How many request-amounts to deposit at once when opening an EVM batch-settlement channel.; MCP_BRIDGE_MAX_DEPOSIT_ATOMIC: Hard cap in atomic units on a single batch-settlement channel deposit or top-up.; X402_MCP_BRIDGE_CHANNELS_DIR: Directory for persisted batch-settlement channel state (survives client restarts).; RPC_URL_8453: Per-chain RPC override, one variable per chain id (RPC_URL_ , e.g. RPC_URL_8453 for Base). Defaults to viem's public RPC for that chain..

Before connecting

Check the maintainer’s instructions for account access, authentication and the supported client configuration. Once connected, inspect the tools your client receives and try a small task that matches the server’s stated purpose. The registry description does not include a verified, complete tool list.

Project and source

View the publisher’s registry entry · Project repository · Project website. This profile uses version 1.0.2 from the registry. Registration identifies the publisher namespace; it does not establish that this is a first-party integration for every service it connects.

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