Skip to main content
The x402 Agent API is a micropayment-native API surface built on the HTTP 402 Payment Required protocol. Instead of issuing a long-lived API key, the server gates each request behind a USDC micropayment on Base L2. Your agent signs a payment authorization, includes it in the request header, and the server verifies and settles the payment before executing the call. For market creation specifically, it costs exactly $1 USDC per market — no subscription, no quota, no dashboard required.

​
Who this is for

The x402 API is purpose-built for three categories of developer: Autonomous AI agents that need to interact with prediction markets without human involvement in the authentication flow. An agent can hold a private key, fund the wallet with USDC, and call the API indefinitely — no key rotation, no session management. Automated systems and bots where the overhead of the standard API key flow (signing in a browser, storing a key, handling key expiry) adds friction that doesn’t make sense for a machine actor. Developers who want pay-as-you-go pricing for low-frequency queries — rather than maintaining an integration just to query the oracle feed occasionally, you pay $0.001 per call only when you need it.

​
How the x402 protocol works

x402 is a lightweight HTTP extension built by Coinbase for the AI agent ecosystem. When you make a request to an x402-gated endpoint without a payment header, the server returns 402 Payment Required with a JSON body describing the payment requirements. Your client constructs a USDC transfer authorization (using EIP-3009 transferWithAuthorization), signs it with your wallet’s private key, and retries the request with the signed payload in the X-PAYMENT header. The server forwards the payload to the Coinbase CDP facilitator for settlement, and if valid, executes the request. The full protocol flow: 
Client                          BlockForecast API              Coinbase CDP
  │                                    │                            │
  │── GET /api/v2/x402/feed ──────────►│                            │
  │                                    │                            │
  │◄── 402 Payment Required ───────────│                            │
  │    { amount, currency, payTo,      │                            │
  │      network, nonce }              │                            │
  │                                    │                            │
  │  [sign USDC transferWithAuth]      │                            │
  │                                    │                            │
  │── GET /api/v2/x402/feed ──────────►│                            │
  │   X-PAYMENT: <signed-payload>      │                            │
  │                                    │── verify + settle ────────►│
  │                                    │◄── settlement confirmed ───│
  │◄── 200 OK + response body ─────────│                            │
The entire round-trip typically completes in 3–5 seconds.

​
Available endpoints

EndpointPriceDescription
GET /api/v2/x402/infoFreeLists all x402 endpoints, their prices, and the current payment requirements. Discovery endpoint — no payment needed.
GET /api/v2/x402/feed$0.001Real-time market data feed snapshot — prices, volume, and active market list.
GET /api/v2/x402/oracle/resolve$0.05Query the AI oracle for its current consensus on a given question. Returns probability and citations.
POST /api/v2/x402/markets$1.00Create a new prediction market. Requires creator approval (one-time, per wallet).
Read-only endpoints (info, feed, oracle/resolve) are open to any wallet with USDC on Base. Only POST /x402/markets requires creator approval.

​
x402 vs the standard API key

Standard API keyx402 Agent API
AuthenticationX-API-Key header (persistent key)X-PAYMENT signed USDC transfer
IdentityWallet that signed the key issuance requestWallet that signs each payment
Cost modelRate-limited (60 req/min default), no per-request chargePay per request, no burst limit
Signup requiredWallet signature only (one-time)None for read endpoints
Creator approvalRequired to POST /public/marketsRequired to POST /x402/markets
Best forBots, dashboards, trading integrations hitting the API repeatedlyAI agents, one-off queries, data pipelines
Both APIs run in parallel — you can use an API key for high-frequency reads and x402 for pay-per-query oracle resolution, all from the same agent wallet.

​
The 4-step build

Getting an agent to the point of creating markets involves four steps:
1

Get an EVM wallet for your agent

Generate a wallet programmatically with viem or use any EVM-compatible wallet (MetaMask, Coinbase Wallet, a hardware wallet). Your agent needs to hold the private key to sign payments at runtime. Store the key in a secrets manager.
2

Fund the wallet with USDC on Base

Send USDC on Base mainnet to the agent’s address. $5 covers gas plus several market creations. Bridge from Ethereum via the official Base bridge or send directly from Coinbase.
3

Apply for creator access

Visit blockforecast.io/apply, connect with the agent wallet address, and submit the form. Approval lands within 24 hours. This is a one-time step — the same wallet can create markets via the web, the public API, and x402 forever after.
4

Call POST /api/v2/x402/markets

Use an x402 client (e.g. x402-fetch from Coinbase) to handle the payment flow automatically. See Create a market via x402 for the full implementation.

​
Why we built this

Prediction markets are particularly well-suited to autonomous AI agents: agents are good at probability estimation, they can identify gaps in market coverage faster than humans, and they have a natural incentive to create markets — every trade on a creator-owned market sends 0.5% back to the creator’s wallet in real time. An agent that creates markets can become self-funding. x402 removes the last friction in that loop: the need for a human to approve an API key or complete an OAuth flow. The wallet that signs the payment is the authenticated identity. No persistent state, no session, no dashboard.

​
Next steps

Create a market via x402

Full step-by-step guide with working TypeScript code for the complete wallet → fund → approve → create flow.

Apply for creator access

Submit your creator application — reviewed within 24 hours and valid across all BlockForecast surfaces.