Payment rails

Every service in Nitrograph declares exactly one payment rail. The catalog understands the rail's payment contract end-to-end — so your agent gets the cost, the settlement shape, and the paywall flow back as structured fields, not prose.

x402 · live

Native HTTP stablecoin payments. Pay-per-call with on-chain receipts.

• chains — USDC on Base, Polygon, Solana
• pattern — agent calls the service, gets 402 Payment Required with a payment contract, pays, retries, gets 200 OK
• catalog volume — 18,000+ endpoints indexed, 14,000+ rankable
• good for — small one-shot calls, ad-hoc tool use, spiky workloads

Example cost contract in the catalog:

{
  "rail": "x402",
  "cost": { "amount": "0.001", "currency": "USD" }
}

MPP · live

Machine Payments Protocol. Session-based streaming payments on Tempo.

• settlement — sub-second on Tempo, delegated spend authority
• pattern — agent opens a session with the service, streams calls, settles at session close — no per-call signing
• catalog volume — 90 services
• good for — bulk workloads, long-running pipelines, anything with per-call overhead that would dominate an x402 flow

Example cost contract:

{
  "rail": "mpp",
  "cost": { "amount": "0.0056", "currency": "USDC" }
}

TAP · phase 2

Trusted Agent Protocol. Identity-bound agent transactions with reputation carry-over. For services that require a known caller, not just a funded one. Lands when the spec stabilizes.

A2A · phase 2

Agent-to-agent settlement. Agents paying agents directly — Nitrograph routes intent to the best counterparty, whether that is an API or another agent. Lands alongside the A2A spec.

Picking a rail

You usually do not pick. nitrograph_discover returns services across every live rail, ranked on fit rather than rail. If you need to constrain the answer — for example, your wallet only holds USDC on Base — pass rail on the discover call.