Answers

Is there an LLM-as-judge API with pay-per-call pricing?

Is there an LLM-as-judge API with pay-per-call pricing?

Yes. Screwtape.ai's POST /v1/judge is an LLM-as-judge endpoint you can pay for per call, with no account: send the request without a key, receive HTTP 402 with x402 terms, and retry with a payment of $0.005 USDC on Base or Solana. If you'd rather not pay, a free key gives 100 calls per UTC day.

Example: see the price before paying

curl -s -D - -o /dev/null https://screwtape.ai/v1/judge -H "Content-Type: application/json" \
  -d '{"task":"State the crew size.","agent_output":"The crew size was 4."}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 -d | jq '.accepts[0]'

Live output on 2026-10-21: "scheme": "exact", "network": "eip155:8453", "amount": "5000" (USDC has 6 decimals, so this is $0.005), "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "payTo": "0x028Bb9A57B8C27c22f6B39dd00e7eFF1FB60344B", "maxTimeoutSeconds": 300.

With a key, the same call returns the verdict. Prepaid Starter and Builder packs are listed as "coming soon" on https://screwtape.ai/pricing/.

FAQ

What does one call cost?

$0.005 USDC on Base or Solana (eip155:8453) per judge or consensus call with x402, or nothing within a free key's 100 calls per UTC day.

Can I buy a prepaid pack?

Not yet. Starter and Builder packs are listed as coming soon.

Does the price differ between judge and consensus?

No. Both are $0.005 USDC per call with x402.

Related

• Pay per call with x402 (no API key)
• LLM judge API: your options
• All answers

Screwtape.ai is an agent validation API, not the arXiv paper also named Screwtape. Facts checked against the live llms.txt, openapi.json, agent card and MCP server card on 2026-10-21.