Skip to main content

​
What is x402?

x402 is an open HTTP payment protocol. When a server needs payment before serving a request, it returns an HTTP 402 Payment Required response with machine-readable payment instructions. The client pays, then resubmits the request with a payment receipt. Float uses x402 as the payment rail for all agent-to-API transactions. 
agent → GET /api/data
          ← 402 Payment Required
             { "amount": "0.05", "currency": "USDC", "recipient": "SolAddress..." }

agent → pays 0.05 USDC on Solana
agent → GET /api/data
         X-Payment: <receipt>
          ← 200 OK + data
Everything happens automatically. The agent never stops to ask you for approval.

​
Why x402?

Traditional API access requires:
  1. Create an account on the provider’s site
  2. Generate an API key
  3. Add the key to your environment
  4. Hope your agent doesn’t leak it
x402 replaces all of that with a single USDC payment. No accounts, no keys, no paywalls. For AI agents specifically, x402 is the correct abstraction — agents understand money better than they understand authentication flows.

​
How Float implements x402

Float wraps x402 in a higher-level abstraction so your agents don’t need to implement the protocol themselves:
  1. Probe — the agent calls a Float-registered service endpoint
  2. 402 received — Float intercepts the 402 response
  3. Payment — Float deducts from the agent’s wallet and broadcasts a Solana transaction
  4. Resubmit — Float attaches the X-Payment header and resubmits the request
  5. Done — the agent receives the 200 OK response as if nothing happened
Your agent writes one line. Float handles the rest.

​
The X-Payment header

After payment, Float attaches a signed receipt in the X-Payment header: 
X-Payment: v1.<base64-encoded-receipt>
The receipt contains:
  • Transaction signature (Solana)
  • Amount and currency
  • Timestamp
  • Recipient address
The API server verifies this on-chain before serving the response.

​
Supported payment rails

RailStatus
Solana (USDC)Live
Ethereum (USDC)Coming soon

​
x402 service registry

Float maintains a registry of x402-compatible services your agents can discover at runtime using the find_service MCP tool. The registry includes:
  • Float-native services (image generation, AI models)
  • Third-party APIs that have adopted x402
To find what’s available: 
find_service({ query: "weather data" })

​
Further reading