x402 Compatibility

PrivChain aligns to Coinbase x402 as a core protocol requirement.

Why x402

x402 already solves HTTP payment semantics. PrivChain focuses on privacy infrastructure, not transport reinvention.

PrivChain Role in Flow

Agent -> x402 Request -> Resource Server -> PrivChain Facilitator -> Privacy Pool -> Settlement -> Verification Response

Facilitator Endpoints

• POST /verify - validate payment payload against privacy state
• POST /settle - submit shielded settlement transition
• GET /health - facilitator health and version

Payment Scheme

PrivChain introduces priv-stark/v1 as an x402-compatible scheme.

Expected payload fields include:

• scheme
• network
• commitment
• nullifier
• proof
• amount
• recipient
• expiry

SDK Direction

SDK surfaces should support one-call private payment flows while preserving x402 compatibility.

MCP Direction

MCP tool surfaces should expose private payment and policy-aware controls without bypassing facilitator verification.