We're going to need default hard budget caps on pretty much everything
Simon Willison says APIs need default hard budget caps as AI agents can trigger costly usage.
Simon Willison argues that pay-by-usage services and APIs need default hard budget caps that stop access and return errors after a set monthly amount. Soft caps that only send a warning email will not prevent runaway charges, he writes. Coding agents and personal agents lower the friction of launching code that calls paid APIs or bills for extra storage and compute.
- Hard monthly caps should cut off usage and return errors
- Email-only soft warnings are not sufficient controls
- Coding and personal agents make paid API and compute spend easier to trigger
From the original article
Here's a product feature which the world is going to need a whole lot more of over the coming months and years: default hard budget caps . I'm talking about the feature of pay-by-usage services and APIs that lets you say "after $X/month, cut this thing off and return errors". These need to be hard limits.
simonwillison.net
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