X402 Universal Payer

Host a copy with our keys and logs.

• 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_<chainId>, e.g. RPC_URL_8453 for Base). Defaults to viem's public RPC for that chain.