Spend Brake

About Spend Brake

Spend Brake puts hard dollar caps on every paid API your apps and AI agents call, enforced before the request leaves. Swap one base URL and one key: each call is priced per SKU, checked against your caps in one atomic step, and refused with a clear 402 once a cap would be crossed. Caps apply per org, key, SKU, environment, agent and session, per day and month. Google Maps Platform first, with Twilio, Mapbox, HERE, Tavily, Exa, Brave and SerpApi built in, and any other HTTP API as a custom API. It adds loop detection, a kill switch, and alerts with Kill/Raise/Mute links. New: `brake doctor --prove` checks from the agent's side that nothing can spend past its caps, using a $0 probe. `@spend-brake/mcp` gives agents capped search, Maps and API tools in place of their Tavily or Exa MCP server. Your provider key never leaves the proxy. Hosted, or self-hosted under Apache-2.0.

What Spend Brake is used for

• Give a coding agent a budget it cannot exceed
• Swap a Tavily/Exa MCP server for capped search
• Stop a runaway loop from running up a Google Maps bill
• Cap test suites and staging that hit paid APIs
• Check an agent can't bypass its caps (brake doctor)

Spend Brake pricing

Freemium. Free: $0, 1 key, 1 provider, up to $50/month of protected spend, no card. Indie $9/mo, Team $49/mo, Agents $149/mo. Self-hosted core is free under Apache-2.0; Business license $299/mo, Enterprise from $10,000/yr. USD, before tax.

Spend Brake alternatives

Tools the builder names as the closest alternatives.

• Google Cloud Billing budgets
• LiteLLM
• Portkey
• Helicone
• Lunar.dev

Spend Brake FAQ

Can spend go over a cap?

By at most one request's worst case. Each request reserves its worst-case cost against every cap before it is forwarded, so parallel requests cannot slip past together.

What happens when a cap is reached?

The proxy answers 402 budget_exceeded with the scope, cap, amount spent and reset time. The provider never sees the request.

Does Spend Brake cache or store responses?

No. Responses stream through and are never stored. Only request metadata is kept, never bodies or query strings.

Can an agent raise its own cap?

Not with a session key: it can only spend. Keep the admin token out of its reach; brake doctor checks for that and for raw provider keys it could use directly.

Does it cover the Maps JavaScript API?

No. Client-side Maps (JavaScript API, tiles, widgets) is out of scope; Spend Brake proxies server-side APIs.