tool design

Sierra's signature design exercise. The grading hinges on three things most candidates underweight: tool API shape, the read/write trust boundary, and eval cases written before the agent. Walkthrough inside.

An Anthropic-signature integration question. The hidden rubric: tools are a curated product surface, not a proxy for your OpenAPI spec, plus the auth model and confused-deputy trap most candidates miss.

Untrusted content plus write-capable tools is the lethal combination. Prompt-level defenses alone fail this question; the winning answer is an architecture where injection succeeding still can't move money.