How Does a Spend Firewall Work?
A spend firewall sits between your agent and the money: it evaluates every proposed transaction before settlement and returns a deterministic decision.
The decision
Every spend attempt is evaluated against your rules: caps, allowlists, velocity limits, categories, time-of-day, approval thresholds.
The outcome
APPROVED: let it through. BLOCKED: stop it. FLAGGED: pause for a human.
The audit
Every decision is logged with the rule that fired — a complete, queryable trail.
At a glance
| Layer | Job |
|---|---|
| Rules engine | Evaluate the transaction |
| Decision | APPROVED / BLOCKED / FLAGGED |
| Audit log | Record every decision |
FAQ
How fast is it?
~5 ms — deterministic rules, no model in the path.
Why deterministic?
Rules can't be argued with or injected; a model-based path can.
Related
Stop the next $12,400 night.
One API call (or MCP tool) in front of every agent transaction — APPROVED, BLOCKED, or FLAGGED, deterministic, ~5 ms, fully logged.
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