Checks that spend money
Three checks settle or attempt real payments. Each call spends; repeated calls spend repeatedly.
| Check | What it does |
|---|---|
X402-06 | Settles a valid x402 payment against the target |
X402-07 | Attempts a payment with a deliberately corrupted signature |
MPP-01 | Settles a full MPP charge-mode payment |
This is inherent to what they verify rather than an implementation choice: a payment flow that was never exercised cannot be verified on-chain, and charge mode has no dry run.
The default posture is the cheap one. X402-06 and X402-07 are skipped
entirely when no payer key is present, and --read-only (CLI) or
readOnly: true (MCP) restricts an x402 run to the free checks. MPP-01 has
no read-only mode and always spends when it runs.
Over MCP these tools declare idempotentHint: false and say plainly in their
descriptions that each call spends, because an agent needs to know that before
deciding to retry on timeout or run a suite in a loop. An agent that retries a
spending check will drain the payer account, at which point every MPP check
fails for reasons that look nothing like the cause.