Spend Firewall RFP Checklist
Buying a spend firewall? Ask these questions — the answers separate a decision engine from a dashboard.
The checklist
1. Decision path: deterministic rules or model-based? (Deterministic can't be injected.)
2. Latency: what's the p95 decision time? (~5 ms target.)
3. Rule types: caps, velocity, allowlists, categories, time-of-day, approvals?
4. Audit: is every decision logged with the rule that fired?
5. Pricing: per-call metering or flat? Any overage tier?
6. Deployment: hosted, self-host, or both? License?
7. Integration: HTTP, MCP, CLI — and wrappers for your stack?
8. Rail support: does it sit in front of x402, AP2, AgentKit?
How to score
Weight by your priorities — for most teams: deterministic path, flat pricing, audit log.
FAQ
Why does deterministic matter?
A model-based decision path can be argued with or injected; rules can't.
What's the most underrated item?
The audit log — it's what answers questions six months later.
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.
See plans — from $99/mo Try a live check