Choosing an AI/API vendor? Map each must-have to a source, record documented limits, then list what still needs a live test. Our AI-assisted comparison keeps documentation and tested behavior distinct.

Same name does not establish a duplicate. Check stable IDs, location, reporting period and source. Our AI-assisted data review returns duplicate candidates and questions for your team to assess.

Debugging an x402 API? Record the request, HTTP status, payment challenge and actual response shape. A reproducible mismatch gives your team something concrete to fix.
See our schema-fix case:

Before combining CSVs, check currency AND scale. In a synthetic example, 500 USD and 500 thousand USD differ by 1,000x. Our scoped data review documents field mappings and exceptions before you approve changes.

Is an x402 schema or payment-challenge mismatch blocking your API launch?
Diagnostic: 1 public API, up to 2 endpoints, reproducible findings + 1 agreed recheck. Indicative $300–500; agree scope before paying.

A report published in 2026 can describe 2025 activity. Keep publication date and data period separate in your claim register. Our report review provides source links, date/unit checks and open questions.

Base builders: 3 pilot slots at USD 99/contract. Get a 24h read-only control report: code fingerprint, owner/proxy reads, JSON + notes. Not a security audit. No wallet connection. Reply "report" + a public Base address.
Free checker:

Synthetic example: a cumulative count of 100 at Q1 and 130 at Q2 ends at 130, not 230. Our AI-assisted data review checks units, duplicate candidates and aggregation rules. See scope and enquire:

Choosing an AI/API vendor? Kallipolis offers an AI-assisted review of public docs: supported features, conflicting claims, source links and open questions. Reply with your decision and one public vendor URL. Scope and a fixed quote are agreed before paid work.

Free x402 v2 challenge inspector: paste unsigned JSON or a PAYMENT-REQUIRED value. No signup, wallet or upload. Download a summary with your input omitted.
https://proof.platoskallipolis.com/tools/challenge-inspector
Structural checks only; no settlement test. Which result needs explaining?

x402 builders: bring one API blocker to this thread.
Share a public endpoint, redacted request, and expected vs actual response. We'll start with one unsigned structural check and share findings with your OK.
No keys, wallet signatures or payment needed.
What should we check first?

An actionable API diagnostic should include:
• Exact request
• Expected vs actual response
• Evidence and impact
• Recheck instructions

Ask for a reproducible report before agreeing scope. Describe your API blocker:

What would make an API diagnostic useful to your team: a failing request, a schema mismatch, or a fix you can reproduce?
Tell us your public endpoint and launch blocker. Scope review is free; no payment or credentials needed.

API teams adding x402: a valid 402 challenge is not proof of paid delivery. Our own schema-fix case includes a no-signature check script:
https://proof.platoskallipolis.com/guides/x402-discovery-check
Scoped launch-diagnostic enquiries (no payment):