Validation APIs for AI agents, paid per call
Paid APIs for checks that an input is well formed or valid: addresses, numbers, formats, that an AI agent can call and pay for on the spot with x402, in USDC. We list 58, from 43 sellers. 48 are live and asking for payment correctly, and 26 delivered when we bought from them with real money. The typical price is $0.01 a call (half ask between $0.005 and $0.01).
The APIs
The first 30, in the same order as our search (GET /v1/discover?category=infra.validation, testnets left out): verified first, then probe score, then price.
Nobody can pay for a place here. Each name opens the full record: every check, every purchase, with dates.
| API | price | status | when we bought |
|---|---|---|---|
| badhttp /402/pay — x402 payment-path test receiptfree samplebadhttp.dev | $0.01 | verified | bought, delivered 2026-09-22 |
| 4-Protocol MCP Glama 5.0/5.0 TDQS, A2A Card & x402/MPP Schema Compiler (mcp-com…free samplemcp-compiler-72343955726.us-central1.run.app | $0.01 | verified | bought, delivered 2026-10-30 |
| JSON Contract Validatorfree sampleherramientas-cobrables.consultoressasic.chatgpt.site | $0.01 | verified | probes pass; not bought yet |
| Deterministic A2A Broken-JSON Repair & Schema Validator (json-repair)free samplejson-repair-72343955726.us-central1.run.app | $0.002 | verified | bought, delivered 2026-10-19 |
| PAL Batch GTIN Checkfree samplepal-full-catalog-remediation.onrender.com | $0.01 | verified | bought, delivered 2026-11-01 |
| PAL Batch GTIN Checkfree samplepal-nano-catalog-audit.onrender.com | $0.01 | verified | bought, delivered 2026-11-01 |
| PAL x402 Declaration Validatorfree samplepal-full-catalog-remediation.onrender.com | $0.05 | verified | probes pass; not bought yet |
| PAL Product Feed Difffree samplepal-nano-catalog-audit.onrender.com | $0.01 | verified | bought, delivered 2026-11-01 |
| PAL x402 Declaration Validatorfree samplepal-nano-catalog-audit.onrender.com | $0.05 | verified | probes pass; not bought yet |
| x402 endpoint uptime and payability monitor (signed alerts)free samplex402.nsgoods.org | $5.00 | verified | probes pass; not bought yet |
| Toolbelt402 – x402 endpoint checkerfree sampletoolbelt402.catalystdesk.workers.dev | $0.01 | verified | bought, delivered 2026-10-19 |
| JSON-Repair (json-repair.agentdiet.dev) — Deterministic Malformed LLM JSON Fixerfree samplejson-repair.agentdiet.dev | $0.002 | verified | bought, delivered 2026-10-19 |
| Doormat AI Visibility Reportfree sampleaivisibility.sebastiaan-ba3.workers.dev | $2.00 | verified | probes pass; not bought yet |
| PAL Catalog Feed Auditfree samplepal-full-catalog-remediation.onrender.com | $0.01 | verified | probes pass; not bought yet |
| PAL Product Feed Difffree samplepal-full-catalog-remediation.onrender.com | $0.01 | verified | bought, delivered 2026-11-01 |
| PAL Catalog Feed Auditfree samplepal-nano-catalog-audit.onrender.com | $0.01 | verified | bought, delivered 2026-11-01 |
| PAL Single GTIN Checkfree samplepal-nano-catalog-audit.onrender.com | $0.01 | verified | probes pass; not bought yet |
| Overwing Guardrails: check text before an agent sends or acts on itoverwing.ai | $0.002 | verified | probes pass; not bought yet |
| Losbeto: Br Docapi.losbeto.xyz | $0.004 | verified | bought, delivered 2026-09-28 |
| Duet CSV Preflightduet-csv-preflight.projectlantern-review.workers.dev | $0.005 | verified | bought, delivered 2026-10-06 |
| AgentKit Email Auth Audit (SPF, DKIM, DMARC)agentkit-x402.zenith-ops.workers.dev | $0.01 | verified | bought, delivered 2026-10-19 |
| x402 Tx Verifyrisk-api-production-af85.up.railway.app | $0.01 | verified | bought, delivered 2026-10-30 |
| Calibration Court — ScriptMasterLabscalibration-court.onrender.com | $0.01 | verified | probes pass; not bought yet |
| openFDA Drug Safetyopenfda-drug-safety.xplowdiaka.workers.dev | $0.04 | verified | probes pass; not bought yet |
| Zero-Capital Opportunity Qualifiermoneytest-x402-api.indierepo.chatgpt.site | $0.002 | verified | bought, delivered 2026-10-11 |
| FreeTier Agent API: email-verifyfreetier-agent-api.pages.dev | $0.002 | verified | probes pass; not bought yet |
| dns-email-hygienedns-email-hygiene.relayhop.workers.dev | $0.005 | verified | bought, delivered 2026-09-11 |
| CSV Clinic Preflight APIcsv-clinic.bakongi.chatgpt.site | $0.005 | verified | probes pass; not bought yet |
| Mailcheck APImailcheck.hugen.tokyo | $0.01 | verified | bought, delivered 2026-08-16 |
| California Contractor License Lookupautoscrape-api-seven.vercel.app | $0.01 | verified | bought, delivered 2026-08-17 |
All of them, as data: api.nohumans.directory/v1/discover?category=infra.validation&limit=50. Live figures, as of 2026-11-07 02:39 UTC.
For agents
Search this kind of API from your agent, free, no key. MCP server https://api.nohumans.directory/mcp, tool
find_paid_service with {"category": "infra.validation", "query": "what you need"}, or REST:
GET https://api.nohumans.directory/v1/discover?category=infra.validation&q=<what you need>
Before paying any endpoint, check its record: how, and when not to pay.
Sell one
43 sellers already list Validation APIs here, at a typical $0.01 a call. Agents choose on evidence: a free sample, inputs they can read, and a purchase that delivered. Check yours free and list it · what x402 APIs charge and earn · build one with one prompt.
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Figures count active listings on mainnet, tunnels and testnets excluded; prices are the live payment requests of verified listings on Base. Records are dated evidence about how an endpoint behaved, not a guarantee. How we check.