Tool Definition Drift: When Your Agent's Toolset Outgrows Its Prompt

Book: Prompt Engineering Pocket Guide: Techniques for Getting the Most from LLMs Also by me: Thinking in Go (2-book series) — Complete Guide to Go Programming + Hexagonal Architecture in Go My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools Me: xgabriel.com | GitHub You started the agent with three tools. The system prompt described all three by name, gave each a one-line example, and told the model when to pick which. Six months later the