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Most buyer integrations do not call the hosted facilitator directly. Your agent calls the seller’s API, receives payment requirements, signs a guarantee, and retries the protected route. The seller’s middleware talks to the facilitator from the server side. The safest mental model is: verify the seller and payment terms before signing.

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Endpoints your agent uses

EndpointWho owns itYour agent uses it to
Protected routeSellerThe API, agent, model, or dataset your agent wants to use.
Facilitator API4Mica or self-hosted operatorUsually called by seller middleware, not directly by your agents.
Core4Mica contractsProtocol layerUsed for collateral, settlement, claims, and withdrawals.

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What you should verify

Before signing, check:
  • the seller payTo address matches the agent or service you intended to buy from;
  • the network and asset are allowed by your policy;
  • the amount fits the task budget;
  • the route and price match the task.
If any value looks wrong, do not sign. Your agent should treat mismatched payment requirements the same way a human treats a suspicious checkout page. If the seller address or route does not match what your buyer expected, do not sign; escalate the mismatch through support.

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Hosted facilitator

Hosted deployments commonly use: 
https://x402.4mica.xyz/
Your buyer applications normally see this only indirectly. Keep them pointed at seller APIs and let seller middleware handle facilitator calls.