x402 in Primitive402

Flow

1. An agent discovers a tool through the catalog, OpenAPI, MCP, or docs.
2. The agent calls an /x402/v1/... alias.
3. Primitive402 returns HTTP 402 Payment Required with payment requirements.
4. An x402-capable client pays with USDC and retries to receive structured JSON.

The current public beta network is Base Sepolia. Production or mainnet payment setup may evolve.

The current public beta asset is testnet USDC. Treat beta payments as testnet-only and do not send mainnet funds.

The x402 payment-required payload includes network, asset, amount, payTo, and resource metadata used by compatible clients.

Expected unpaid call

curl -i https://primitive402.dev/x402/v1/extract-subscription-terms \
  -H 'content-type: application/json' \
  -d '{
    "url":"https://stripe.com/legal/subscription-policy"
  }'

HTTP 402 Payment Required

Public beta payment verification

Primitive402 has completed end-to-end paid x402 testnet calls on Base Sepolia. The verified sequence was: unpaid request, HTTP 402 Payment Required, Base Sepolia USDC payment, retry, then HTTP 200 with the same structured JSON response shape as the tool's local route.

Internal metrics showed paidX402Calls incrementing after settled paid calls. The current public beta uses Base Sepolia testnet USDC, and the mainnet or payment-provider setup may evolve before production billing.

Verification metadata: network eip155:84532; asset 0x036C...CF7e; seller/payTo 0x1e8c...59ab; buyer 0x6cE9...59db.

Charging policy

• HTTP 402 Payment Required challenges are not charged.
• Successful paid 2xx tool responses are counted as charged and increment paidX402Calls.
• Validation errors, unsafe URL blocks, rate limits, server errors, and failed tool executions are not counted as successful paid calls.
• Free-route 429 responses increment rateLimitedCalls, not paymentRequiredCalls or paidX402Calls.
• Low-confidence HTTP 200 responses may still be charged because they are valid analysis results.
• The public beta uses Base Sepolia testnet USDC. Mainnet or payment-provider details may change before production billing.

The x402 middleware verifies payment before Primitive402 route handlers run. Request validation, SSRF protection, tool execution, and final response status happen after that middleware. If a paid beta retry settles but the handler later returns a non-2xx response, Primitive402 does not count it in paidX402Calls; this beta does not attempt automatic refunds.

Troubleshooting

• If a free route succeeds but an x402 route returns 402, inspect the payment-required response and retry with a valid payment header.
• If a wallet or facilitator rejects payment, confirm Base Sepolia, testnet USDC, amount, and recipient metadata.
• If the response is not JSON, verify content-type: application/json and that the request body matches the tool schema.

Discovery

For external marketplace checks, see Discovery readiness.