Comparison · verified 2026-07-27

x402 Validator vs x402 Doctor

x402 Doctor by Stelar Digital is a free, quick endpoint checker. x402 Validator (this service) is a strict-v2 conformance engine. They overlap on the basics and diverge on depth. Everything below comes from both products' own public pages and repos.

What each one runs

Capability	x402 Doctor	x402 Validator
Reachability probe	✓	✓ (every check)
Bot-wall / Cloudflare challenge detection	✓	✓ `bot_wall` (added in 0.5.0 — credit where due: their writeup identified this failure mode well)
Returns HTTP 402	✓	✓
402 body parses as JSON object	✓	✓ `json_resilience` (CRITICAL_FAIL on primitives)
`x402Version` present / recognized	✓	✓ `accepts_completeness`
`accepts[]` completeness (scheme, network, amount, payTo, resource)	✓ presence	✓ presence + atomic-units validation (flags `"0.005"` as dollars, off by 10⁶) + `resource.url` must match the probed URL
CAIP-2 network validation	✓	✓ `caip2_compliance` — reads v2 `accepts[].network` (not just top level) and falls back to manifest-declared networks on free-discovery roots
Bazaar input schema (`extensions.bazaar.info.input`)	✓ presence	✓ shape-validated against real production captures, per paid product
Discovery doc (`/.well-known/x402`) exists	✓	✓ `manifest_discovery` + `discovery_resource_listing` (paid resource must actually be listed in it)
Marketplace catalog walk (per-product 402 validation)	—	✓ marketplace mode: every product in the manifest gets its own endpoint audit + bazaar check
Batch audits (many endpoints, one call)	—	✓ CLI + API
Embeddable engine (PyPI package)	—	✓ `pip install x402-conformance-suite`
MCP server (agent-native tool)	—	✓ `x402-mcp`
GitHub Action (CI conformance gate)	—	✓
Free tier	10 checks/min	3 audits/day per IP, then Pro from $9/mo
Open source engine	checker not published	Apache-2.0, full repo, 203 tests

Where x402 Doctor wins

Free tier generosity. 10 checks/minute beats our 3 audits/day for quick iteration. Their checker is the fastest way to sanity-check a fresh endpoint.
Content. Their pricing research and honest-numbers pages are some of the best reading in the x402 space. Their bot-wall writeup in particular names a failure mode most validators ignored — we added bot_wall in 0.5.0 partly because of it.
Setup service. They sell done-for-you x402 wiring ($149). We don't; we sell the audit engine, not consulting.

Where x402 Validator wins

Depth per endpoint. Presence checks tell you a field exists; conformance checks tell you it's right — atomic units, CAIP-2 inside v2 accepts[], resource/URL match, catalog listing.
Marketplaces. If your catalog page is intentionally free (HTTP 200) and only products are paid, a root-URL checker fails you. Our marketplace mode walks every product's own 402 and validates each one.
Embeddable everywhere. PyPI library, MCP server, GitHub Action, batch CLI — the engine runs in your CI and your agent framework, not just a web form.
Verifiable correctness. The engine is open source with 203 tests. When we shipped a CAIP-2 parser bug that false-failed v2 endpoints, a merchant reported it and we fixed, published, and emailed corrections the same day (details on /open).

One fact worth knowing about their starter kit. Stelar's x402-starter-kit ships verify_payment() as a deliberate stub — it accepts any non-empty X-PAYMENT header. Their README says so plainly (credit for honesty), but any endpoint deployed from that kit without replacing the stub is not actually charging anyone. Whichever tool you use: run it against a real endpoint before you trust the paywall.

Run a free audit — 3/day