The most common agentic system failure I encounter in production is not a bad prompt. It is not a context overflow. It is a tool that changed without its registration changing.
I have seen this cause weeks of debugging in systems that were working fine until they weren't — and because the failure is silent, teams often spend time looking at the model first.
What Tool Schema Drift Looks Like
Most agentic frameworks let you register tools with a name, a description, and a JSON schema for parameters. The model reads the description to decide when to call the tool. It reads the schema to know what parameters to send.
# Initial registration — looks fine
