| name | veil-private-pay |
| description | Pay on Stellar privately and without custody. Use when an AI agent needs to send USDC to a payee while keeping the amount, the recipient, and the agent→payee link hidden (zero-knowledge), under a scoped key it cannot drain. Triggers on "pay privately", "private payment", "pay this scan key", "veil pay". |
Veil — private payments for autonomous agents
Veil lets an agent pay in USDC on Stellar so who was paid, how much, and that two
payouts came from the same agent never touch the chain (a Groth16 ZK proof), while
the agent acts under a scoped SessionAccount key it cannot drain (autonomy without
custody). Settlement is a metered x402 call.
How to use it
The Veil MCP server exposes these tools (connect via the config in
deploy/veil.mcp.json — set the URL to your deployment, e.g. https://<host>/mcp):
| Tool | Purpose |
|---|
veil_pool_status | live pool root, leaf count, USDC pooled |
veil_budget | remaining scoped cap on the agent's SessionAccount |
veil_quote | x402 price + nonce for a veil_pay call |
veil_pay | make a ZK-private payment through the SessionAccount (x402-metered) |
workflow_list / workflow_run | run a reusable flow (flagship: pay-if-budget) |
The standard flow (what an agent does)
veil_pool_status / veil_budget — confirm the pool is up and the scoped budget
covers the amount.veil_quote { amount } — get the x402 price + a one-time nonce.- Pay the x402 fee on-chain (a tiny native payment to the operator, memo = the
nonce). See
payX402() in agent/x402.ts.
veil_pay { recipientScanKey, amount, payment: { nonce, txHash } } — the server
verifies the fee on Horizon, then makes the ZK-private deposit through the
SessionAccount. Returns { commitment, tx }.
Or do it in one call: workflow_run { name: "pay-if-budget", recipientScanKey, amount }
— budget-gate → ZK deposit → confirm.
Guarantees (why this is safe to give an agent)
- Can't drain: the SessionAccount
__check_auth allows only Veil.deposit into
one pool, only USDC, up to a cap, before an expiry. Anything else reverts on-chain.
- Can't be seen: each payment is a Groth16 membership proof over BN254 — the chain
stores only commitments, a Merkle root, and nullifier hashes.
- Can't be redirected: the payout address is bound into the proof.
Testnet only. The reference driver is scripts/agent-pay.ts; the LLM-driven client is
agent/demo-agent.ts.
