x402 payments

x402 uses HTTP 402 Payment Required as a machine-readable payment negotiation. For The Spawn docs, the user-facing explanation is:

Charge for one tool call without forcing a subscription, API key, or account setup.

First-run shape

Offer a demo request that needs no wallet.
Return 402 for unpaid paid requests.
Include exact payment requirements.
Let the caller retry after payment and receive a receipt.

Verified unpaid response

curl -i https://socialintel.dev/v1/search \
  -H "Content-Type: application/json" \
  --data '{"query":"yoga","country":"US","limit":1}'

Expected status:

HTTP/2 402
payment-required: <base64 x402 payload>
content-type: application/json

The verified payload included accepted Base USDC and Solana USDC payment options. The Base option used amount 500000, which is $0.50 for a 6-decimal USDC asset.

What to expose

Item	Example
Network	`eip155:8453` for Base
Asset	USDC contract address on Base, or the Solana USDC mint when the service accepts Solana
Amount	`500000` for `$0.50` with 6 decimals
Payee	`payTo` wallet address
Timeout	`maxTimeoutSeconds`
Resource	URL and description
Demo	`?demo=true` or tool argument `demo: true`
Schema	input and output shape

How agents should handle it

An agent should summarize price and payment state before any paid execution:

This call costs $0.50 USDC on Base. Your linked Spawn wallet has 0.00 USDC. Open the funding link, then rerun the same call after the transfer settles.

Do not ask the user to understand raw headers when a simpler approval message is possible.

Start here

Use an agent

Publish an agent

Add payments

API reference

Quality and help

First-run shape

Verified unpaid response

What to expose

How agents should handle it

Next

​First-run shape

​Verified unpaid response

​What to expose

​How agents should handle it

​Next

First-run shape

Verified unpaid response

What to expose

How agents should handle it

Next