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CLAUDEOK142ms
OPUS 4.7$15 / $75per Mtok
CHATGPTOK89ms
HACKERNEWSWhy has not AI improved design quality the way it improved dev speed?14m ago
MMLU-PROleader Opus 4.788.4
GEMINIDEGRADED312ms
MISTRALMistral Medium 3 released6m ago
GPT-4o$5 / $15per Mtok
ARXIVCompositional reasoning in LRMs22m ago
BEDROCKOK178ms
GEMINI 2.5$3.50 / $10.50per Mtok
THE VERGEFrontier Model Forum expansion announced38m ago
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Back to AI agents

x402

The open HTTP standard for machine-payable APIs. Servers return HTTP 402 Payment Required with payment instructions; clients retry with proof of payment. Built for AI agents paying on-chain in seconds.

Origin

x402 was developed by the Coinbase Developer Platform team and published as an open specification at x402.org. It builds on the rarely-used HTTP 402 status code, which was reserved in HTTP/1.1 for "future use" and has finally found its actual purpose: machine-readable payment requirements.

How it works

  1. Request: client GET /api/paid-endpoint
  2. 402 response: server returns { accepts: [{ asset, network, amount, payTo }] }
  3. Payment: client sends on-chain payment to payTo
  4. Retry: client GETs again with X-Payment-Tx: 0x...
  5. Verification: server reads the on-chain receipt, confirms the recipient and amount, serves the data

Discovery in x402 V2

V2 added a discovery extension. Services publish a JSON manifest at /.well-known/x402 that lists every paid endpoint with its accepts block, input schema, and metadata. Facilitators like CDP Bazaar crawl this manifest to auto-index services. TensorFeed's manifest is at /.well-known/x402.

Why it matters for AI agents

AI agents do not have credit cards, signup forms, or copy-paste API keys. The whole stack of traditional payment infrastructure assumes a human at a keyboard. x402 lets agents act on their own spending decisions without a human in the loop, which is the actual unlock for autonomous commerce.

TensorFeed's implementation

TensorFeed supports x402 as a fallback flow on every premium endpoint. Call any /api/premium/* URL without auth, get a 402 with payment instructions, retry with X-Payment-Tx: 0x... and receive both the data and a bearer token for future calls. The agent payments docs walk through it end-to-end.

For repeat use we recommend the credits-first flow over per-call x402: settlement is 50ms instead of 3-5 seconds. But x402 stays available for one-shot discovery calls where the agent doesn't want to pre-commit to credits.

Further reading