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Paid routes return HTTP 402 with a dual challenge so a single request works with either supported protocol. Use any x402- or MPP-aware client.

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The 402 handshake

  1. A plain request to a paid route returns 402 with two headers:
    • WWW-Authenticate: Payment ... — the MPP challenge
    • PAYMENT-REQUIRED — the x402 v2 challenge
  2. Retry the same request through a payment-aware client, or manually with:
    • Authorization: Payment <credential> for MPP, or
    • a PAYMENT-SIGNATURE header for x402 v2.
  3. On success (200), the response includes synthesizedSummary and paymentInfo.
Treat a 402 as a “pay and retry” signal, not a failure. If a plain HTTP request returns 402, retry it through the payment-aware client rather than surfacing an error.

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Pricing: advisory vs authoritative

The OpenAPI discovery document exposes x-payment-info.offers[] on paid routes. These offers are advisory — they may list Base USDC (x402), Tempo, and Stripe charges, or catalog floor prices. The runtime 402 challenge is authoritative. Per-post pricing comes from the live challenge, and the price may scale with content — for example, stock-picks are priced by the number of distinct attributed source articles in the response. Always trust the live 402 over discovery offers.

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Status codes

StatusMeaningAction
200SuccessRead synthesizedSummary and paymentInfo
402Payment requiredRetry the same request through a payment-aware client
403Insufficient purchased credits (API keys)Top up purchased balance
404Content not foundDo not pay; verify the publication / post slugs
429Rate limitedBack off and retry
503Summary not ready (summary_not_ready)Retry later; no payment challenge is issued
A 404 and a 503 never carry a payment challenge — do not pay on either. 503 means the summary is still being generated; retry shortly.

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Discovery

Prefer GET /openapi.json (OpenAPI 3.1) for route shapes, JSON schemas, and paid-route x-payment-info.offers[] metadata. If OpenAPI is unavailable, use GET /.well-known/x402 for the paid resource list in METHOD /path form. The root x-discovery.ownershipProofs field is a Drip vendor extension, not part of core MPP discovery.