# What does this x402 endpoint charge? **Challenge served, decoder refused it.** `https://agent402.tools/api/random` — Invalid PAYMENT-REQUIRED challenge: upstream-schema-invalid ## ENDPOINT | Field | Value | | -------------- | ----------------------------------------------------------- | | URL | https://agent402.tools/api/random | | Canonical | https://agent402.tools/api/random | | Endpoint id | 99baffbc346ca400f386ee79c90beefd | | HTTP status | 402 | | Latency | 260 ms | | Redirects | 0 | | TLS | handshake ok | | Wire form | x402 v2 — PAYMENT-REQUIRED header | | Bytes read | 277 | | Observed at | 2026-08-15T15:14:32Z | | Decoder | refused — TX402_PAYMENT_REQUIRED_INVALID | | Decoder detail | Invalid PAYMENT-REQUIRED challenge: upstream-schema-invalid | ## PAYMENT ⚠️ The decoder REFUSED this challenge. The terms below were parsed from what the endpoint served so that whoever maintains it can see what we saw — they are **not** terms tx402 would pay. | Field | Value | | ----------------------- | ------------------------------------------------------------------------------------------------------------------------ | | Price | 0.001000 USDC | | Amount (atomic) | 1000 | | Scheme | exact | | Network | eip155:8453 · in the tx402 signed manifest | | Asset | USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 · in the manifest | | Pay to | 0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0 | | Pay to declared dynamic | no | | Authorization window | 300s | | Resource | https://agent402.tools/api/random | | MIME type | application/json | | Description | Cryptographically secure randomness. ?bytes=1..1024 returns hex; or ?min=&max= returns a uniform integer; ?count=1..100. | | Facilitator | not observed | ## OBSERVED | Field | Value | | ------------------ | -------------------- | | First seen | 2026-08-15T04:00:12Z | | Last seen | 2026-08-15T15:14:32Z | | Scans recorded | 3 | | Availability (30d) | not measured yet | | Latency p50 | not measured yet | | Changed at | What changed | | -------------------- | ----------------------------------------------------------------------------------------------- | | 2026-08-15T05:00:51Z | first_seen: challenge_hash — → 6729e416f2e15ba301eb7d6560d0cde3e2d532a656eb82fcce390ff6e5926e0c | ## SECURITY **The strict decoder refused this challenge** (`TX402_PAYMENT_REQUIRED_INVALID`), which is the finding that matters most here. 0 failed, 1 warned, 15 passed. Those checks describe what could still be determined from what the endpoint served. A check that could not run reports `skip` and is never counted as a pass. | Check | Detail | | ---------------------------------- | ----------------------------------------------------------------------------- | | pass wire_form_detected | Served as v2-header. | | skip base64_strict | The decoder refused the challenge; the framing cannot be reported separately. | | pass json_wellformed | — | | pass x402_version_known | Declared x402Version 2. | | pass accepts_present | The challenge offers 13 ways to pay. | | pass size_within_limit | Read 277 bytes, within the probe's cap. | | pass network_caip2_wellformed | network: eip155:8453 | | pass network_recognized | Recognized means present in the tx402 signed release manifest. | | pass asset_recognized | Recognized means present in the tx402 signed release manifest. | | pass amount_atomic_canonical | — | | pass amount_positive | — | | pass pay_to_wellformed | — | | warn max_timeout_sane | Authorization window 300s exceeds the tx402 maximum of 60s. | | pass resource_origin_match | — | | pass scheme_known | — | | skip facilitator_known | The challenge named no facilitator. | | pass mime_type_wellformed | mimeType: application/json | | pass extra_wellformed | `extra` carries 2 field(s), preserved verbatim. | | skip amount_within_observed_range | No prior observations of this endpoint. | | skip recipient_matches_observed | No prior observations of this endpoint. | ## RISK — MEDIUM (72/100) score_version `v1` · confidence `static_only` · 12 signals scored A band describes how much of what we check we were able to confirm. It is not a judgement about the operator of an endpoint. | Signal | Weight Finding | | ------------------------------- | --------------------------------------------------------------------------------------------- | | fail challenge_decodes | 25 The challenge does not decode under the strict x402 decoder tx402 uses before paying. | | pass resource_origin_match | 15 The challenge describes the endpoint that served it. | | pass amount_canonical | 12 The amount is a canonical atomic integer. | | pass pay_to_wellformed | 12 The recipient is a well-formed address for the declared network. | | pass network_recognized | 8 The network is in the tx402 signed release manifest. | | pass asset_recognized | 8 The asset is in the tx402 signed release manifest for this network. | | skip facilitator_known | 0 The challenge named no facilitator. | | pass scheme_known | 6 The payment scheme is one tx402 can route. | | pass tls_ok | 5 The endpoint was reached over a valid TLS connection. | | warn timeout_sane | 4 The authorization window is outside the maximum tx402 will sign for. | | pass redirect_scheme_downgrade | 3 No redirect downgraded the connection. | | pass wire_form | 3 The endpoint serves the x402 v2 header form. | | pass amount_magnitude_band | 2 The amount is within the range we see for x402 endpoints. | Methodology: https://tools.tx402.io/methodology?v=v1 ## TEST WITH TX402 Nothing below sends a key anywhere. tx402 commits policy and budget before the signer is reachable, so a refusal is a payment that was never authorized. ```bash npx tx402 call "https://agent402.tools/api/random" \ --max-spend "0.001000 USDC" \ --network "eip155:8453" \ --dry-run # --dry-run stops after the policy decision. Nothing is signed and nothing is spent. ``` ```ts import { createTx402Client } from "tx402"; // Your signer stays in your process. tools.tx402.io never sees a key, // never asks for one, and cannot build a payment. import { signers } from "./signers.js"; const tx402 = createTx402Client({ signers, policy: { maxPerRequest: "0.001000 USDC", allowedDomains: ["agent402.tools"], allowedNetworks: ["eip155:8453"], }, }); // Policy and budget are committed before the signer is reachable, so a // refusal here is a payment that was never authorized. const response = await tx402.fetch("https://agent402.tools/api/random"); ``` ```python from tx402 import Tx402Client, Policy # Your signer stays in your process. tools.tx402.io never sees a key, # never asks for one, and cannot build a payment. tx402 = Tx402Client( evm_signer=evm, policy=Policy( max_per_request="0.001000 USDC", allowed_domains=["agent402.tools"], allowed_networks=["eip155:8453"], ), ) # Policy and budget are committed before the signer is reachable, so a # refusal here is a payment that was never authorized. response = tx402.fetch("https://agent402.tools/api/random") ``` --- | Representation | URL | | -------------- | --- | | HTML | https://tools.tx402.io/inspect?url=https%3A%2F%2Fagent402.tools%2Fapi%2Frandom | | Markdown | https://tools.tx402.io/inspect.md?url=https%3A%2F%2Fagent402.tools%2Fapi%2Frandom | | JSON | https://tools.tx402.io/api/v1/inspect?url=https%3A%2F%2Fagent402.tools%2Fapi%2Frandom | | History | https://tools.tx402.io/history?url=https%3A%2F%2Fagent402.tools%2Fapi%2Frandom | Decoded by `tx402@0.2.0` — the same strict decoder the SDK runs before it pays.