Free tools, pay-per-call, and x402: how Snapback pricing works

Snapback is built for agents that run at scale, so the pricing is built for machines: most of it is free, the paid part is pay-only-for-what-you-use, and you can settle a diagnosis in USDC from an agent wallet with no account and no invoice.

What's free — and stays free

The tools an agent calls most often cost nothing and need no token:

• detect_loop — mid-run, is the agent repeating a tool call? Always free, unlimited.
• budget_guard — mid-run context / token / cost / step checks with concrete suggested actions. No LLM.
• diagnose_infra_error — an instant verified fix for a cryptic infrastructure error across 46 families. No token; library-first (no LLM), LLM fallback only on a library miss.
• search_docs, convert_trace, request_pattern, and live session_start/step/end guardian streaming.

The idea is simple: the cheap, high-frequency safety checks should never be a line item. You only pay for the expensive part — a full diagnosis of a hard failure.

What a Snapback costs

Loop checks are always free and unlimited. Budget-guard checks have their own generous monthly allowance and are free during launch.

Pay-as-you-go, the agent-native way: x402

Most APIs make an autonomous agent stop and ask a human to create an account, add a card, and manage a key. That breaks autonomy. Snapback uses the x402 standard instead — payment happens over HTTP, in the request itself:

1. Your agent POSTs a trace to https://api.snapback.sh/mcp/x402 with no token.
2. The server replies HTTP 402 Payment Required with the price, the USDC contract, the destination address, and the facilitator details.
3. Your agent signs a payment authorization from its wallet and retries with the signed payment attached.
4. You get the verdict. An empty or unreadable trace is never charged.

No sign-up, no dashboard, no stored card. An agent can discover the price and pay it the same way it makes any other call — which is exactly what "pay for what you use" should mean when the customer is software.

Solana and EVM, both supported

A Solana-native agent pays from its Solana wallet; an EVM agent signs an EIP-3009 authorization and pays in USDC on Base. Same diagnosis, same price, whichever chain you're on.

And a self-hosted version is coming

For teams with strict data-residency or air-gap requirements, a self-hosted Snapback is on the way — run the diagnosis engine inside your own environment. If that's a hard requirement, tell us via request_pattern or the site.