Interline (MCP server)

Rail-discovery + future-proof payments for AI agents — as an MCP server.

Two things your agent gets, today:

1. Discover which payment rail(s) any paid endpoint accepts — before paying. (The discovery layer single-rail clients don't have.)
2. Pay through it — non-custodial, your own key, capped.

And the part that pays off across every rail: integrate once. Three rails are live today — x402 (HTTP 402 + USDC) on EVM (Base Sepolia) and on Solana (devnet), plus MPP on Tempo (Moderato testnet) — all behind the same tool. Real on-chain agent-to-agent settles are confirmed on all three. Every future rail drops in with zero code change. Never re-integrate agent payments again — when the next rail ships, your agent already speaks it.

This is not "another x402 MCP." Single-rail clients make you wire up one rail (and re-wire for the next). This is the discovery + routing layer above them — same shape OpenRouter has for models. Non-custodial by design: payments use your own wallet key; this server never holds, sees, or routes funds through itself.

Tools

Install

pip install interline        # (or: uvx interline)

Add to Claude Desktop / Cursor / any MCP client

{
  "mcpServers": {
    "interline": {
      "command": "uvx",
      "args": ["interline"],
      "env": {
        "APV0_BUYER_PRIVATE_KEY": "0x...",   // YOUR wallet key — stays in your env, never leaves your machine
        "APV0_NETWORK": "base-sepolia"        // or "base" for mainnet
      }
    }
  }
}

Local dev (from a clone):

{ "mcpServers": { "interline": {
    "command": "python", "args": ["-m", "mcp_router.server"],
    "cwd": "/path/to/interline-routes",
    "env": { "APV0_BUYER_PRIVATE_KEY": "0x...", "APV0_NETWORK": "base-sepolia" }
}}}

discover_payment_rails needs no key (it only reads the 402 challenge). pay_for_resource needs APV0_BUYER_PRIVATE_KEY (your funded wallet).

Non-custodial guarantee

• The router never holds funds. discover only reads a public 402 challenge; pay signs with your key, locally, bounded by max_price_usdc.
• The fee model (when one exists) is a software/routing fee billed to you, the developer — never a cut of the funds flow. That's the line between software (this) and money transmission (not this).

Status

Three rails live — x402 USDC on EVM (Base Sepolia) and on Solana (devnet), plus MPP on Tempo (Moderato testnet). Real on-chain agent-to-agent settles confirmed on all three. Neutral by construction: discover_payment_rails surfaces any rail an endpoint offers, and each additional rail is a drop-in adapter with no caller change. Built on the interline-routes rail-agnostic core.