API Marketplace for AI Agents

An agent that needs the latest EUR/USD rate should not need an API key, a subscription, or a Stripe account. Today every API assumes a human set up billing first.

Developers list an API and a USDC price. The agent finds “FX Oracle API — $0.001/request”, calls it, receives HTTP 402, pays on Stellar, and gets the result. x402 covers one request. MPP covers a high-frequency session.

Stellar’s x402 path uses Soroban authorization. MPP supports SAC transfers and payment channels, which fits agents that call the same API hundreds of times.

A developer lists an FX endpoint at $0.001. An agent discovers it, pays the 402, and reads the rate. No key is issued.

1. 01

   Developer lists an API and a USDC price

2. 02

   Agent discovers the listing

3. 03

   HTTP request returns 402

4. 04

   Agent pays on Stellar

5. 05

   Service returns the result

• A listing with name, endpoint, asset, and price.
• The API returns HTTP 402 with machine-readable payment terms.
• An agent pays through Stellar and retries.
• The service returns the payload after payment.
• Support x402 for one request and MPP for a session.

• Catalog

  Registers endpoint, price, asset, and seller.

• Receipt

  Records that a payment authorized a response.

• HTTP 402 with Soroban auth via x402
• MPP charge for per-request SAC transfer
• MPP session channels for high-frequency calls

• x402
• MPP
• USDC
• @stellar/mpp

1. 01

   Listing

   A catalog entry: endpoint, USDC price, seller address.

2. 02

   402 + x402

   One endpoint that challenges, gets paid, and returns data.

3. 03

   MPP session

   A second path that opens a channel for repeated calls.

4. 04

   Agent demo

   An agent discovers the FX API and pays without an API key.

• Reputation, discovery, SLA history, and a machine-readable service manifest.

• x402 on Stellar
• MPP
• Soroban docs