fidacy-payment-firewall

Fidacy — the payment firewall for agents

An agent can be prompt-injected or hallucinate into a payment: wrong payee, an inflated amount, or the same invoice paid twice. Your own log is not evidence. Fidacy puts a signed, independently-verifiable verdict on every money-moving action and blocks the bad one before it settles. It moves no money.

When to use this skill

Invoke it the moment you are about to run a tool that moves money or authorizes a payment (pay, transfer, send_payment, checkout, invoice settlement, a Hermes/Lightning send, an AP2 mandate). Also use it to put a signed trust verdict on any high-stakes action you want to be able to prove later.

How to use it

This skill drives the @fidacy/mcp plugin's tools. Wire it into your pre-action / tool-execution hook:

1. Before paying — call request_payment with { payee, amount, currency, purpose, category, idempotencyKey, invoiceRef? }.

   • ALLOW → you get a short-lived signed grant. Only then run the real payment tool, passing that grant to the executor.
   • DENY → do not pay. The response names the violated rule (payee_not_in_allowlist, per_tx_cap_exceeded, duplicate_invoice…). Stop and report it.
   • Always set invoiceRef when you have one: Fidacy enforces one payment per invoice, so a re-presented invoice (even at a different amount, or with case/spacing tweaks) is blocked — the core BEC defense.

2. To see the guardrails — call verify_mandate: returns the active mandate (caps, allowed payees/categories, window) and Fidacy's public key.

3. To prove what was blocked/allowed — call get_audit_proof with the decisionId: returns the tamper-evident, hash-chained proof.

4. For a signed verdict on any action — call assess_action: returns a riskPayloadJws that anyone can re-verify against the public JWKS at https://api.fidacy.com/.well-known/jwks.json. Attach it to the action's audit trail; you don't have to trust Fidacy — you verify the signature.