Parse and validate an x402 PaymentRequired (HTTP 402) response and explain every field. Flags missing economic fields (scheme/network/asset/payTo/amount), number-typed or human-decimal amounts (must be atomic-integer strings), and missing explicit decimals. Provide ONE of: url (does an unpaid GET and decodes the 402), raw (a JSON or base64-encoded-JSON body string), or json (an object). Deterministic; the only network is the optional unpaid GET.

Decode and validate an x402 PAYMENT-RESPONSE, surfacing success, settlement id, payer, network, and amount. Optionally recomputes the on-chain truth: pass rpcUrl + expectedPayTo for a sui:* network (queries sui_getTransactionBlock balanceChanges), or observedBalanceChanges + expectedPayTo for any chain, and it confirms the net balance change to payTo equals the advertised atomic amount (the "recomputed, not trust-the-operator" check). Provide the response via raw (JSON/base64) or json.

Heuristically scan x402 code (a file or directory) for the high-severity classes: hardcoded chain id, hardcoded decimals, magic-number decimal scaling (10**N, 1eN, *1_000_000), human-decimal/float amounts, and literal asset/token addresses. Returns findings with file:line and severity. Heuristic — a documented default may be a false positive; every finding cites a location for human judgement. No network.

Lint a draft scheme spec (markdown) against the bundled scheme_template.md: reports missing/extra template sections and whether the draft pins down the load-bearing concepts a scheme must specify (value/recipient assertion, settlement identifier, replay protection, atomic+decimals amount encoding, verify/settle flow). Reads the bundled corpus; no network.

Structurally validate an x402 extension payload: checks the typed { info, schema } envelope and runs light known-extension field checks (offer-and-receipt, payment_identifier, gas-sponsoring, sign-in-with-x, builder_code). Pass payload as a single entry (with name), an extensions map keyed by name, or an array. Full JSON-schema validation needs the extension’s published schema; this is the structural gate plus a spec pointer. No network.

Drive the x402 conformance sequence against a facilitator. Holds NO keys: automates the 402 negotiation (with resourceUrl), facilitator reachability (GET /supported), and malformed-verify rejection. The keyed steps (verify happy-path, tampered-reject, settle, idempotent re-settle) run ONLY when you supply a pre-signed paymentPayload + paymentRequirements; settle additionally requires allowSettle: true (it settles real testnet value). Assumes the standard facilitator API (POST /verify, POST /settle). Returns a pass/fail/skip line per step.