x402 Payments

Caesar supports x402 so you can pay for research jobs per request without pre-provisioning an API key. The /x402/research endpoint verifies an x402 payment, creates a scoped API key that only works for the resulting ask, and returns that secret in the response. You can then call any standard Caesar endpoint with that key to retrieve results or fetch content.

How the flow works

1. Prepare an x402 payment payload using your wallet or facilitator client (see the x402 quickstart for language-specific helpers).
2. POST to /x402/research with the payment payload and your research request.
3. Receive a response containing the research job ID, status, and a temporary api_key_secret.
4. Use the returned API key as a Bearer token to call standard Caesar endpoints (e.g., GET /research/{id} or GET /research/{id}/results/{resultId}/content).
5. Once the research completes, revoke the key (it is already scoped to the single ask and expires automatically after settlement).

Requesting research with x402

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curl -X POST https://api.caesar.xyz/x402/research \
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     -H "X-PAYMENT: X-PAYMENT" \
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     -H "Content-Type: application/json" \
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     -d '{
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  "query": "Summarise latest developments in perovskite solar cells.",
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  "compute_units": 3,
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  "system_prompt": "Be concise and cite sources."
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}'

The endpoint accepts the same body as POST /research. The key difference is the required X-PAYMENT header:

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POST /x402/research HTTP/1.1
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Host: api.caesar.xyz
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Content-Type: application/json
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X-PAYMENT: {{base64-encoded x402 payload}}
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{
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  "query": "Summarise the latest trends in agentic tooling for autonomous research",
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  "compute_units": 2,
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  "system_prompt": "Return a concise executive summary with bullet-point recommendations."
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}

The service verifies the payment, settles it, enqueues the ask, and returns the temporary key:

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{
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  "id": "f2f6e5db-2c7d-4f56-bb0c-5a6b6a7a9b10",
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  "status": "queued",
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  "api_key_secret": "sk-temp.x402-demo-secret"
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}

Using the scoped API key

Treat the returned api_key_secret exactly like a normal Caesar API key, but remember it is scoped to a single ask. Any request that references the original ask ID will succeed; other operations will be rejected.

$
curl "https://api.caesar.xyz/research/f2f6e5db-2c7d-4f56-bb0c-5a6b6a7a9b10" \
>
  -H "Authorization: Bearer sk-temp.x402-demo-secret"

Troubleshooting

Additional resources