100s of Tools in Your Agent — Here's How to Actually Pick the Right One

The Problem Nobody Talks About You've built an agent. You've wired up 100+ tools. You feel good about it. Then it starts hallucinating. Picking the wrong tool. Collapsing entire workflows over a single misclassified query. The failure isn't the LLM. It's the architecture. My previous post covered a genuine use case I found for Gemma4 — and this is exactly where it fits in. The Naive Approach (and Why It Fails) Load all tools into LLM context and let it decide. Sounds simple. It is. And it breaks at scale. Hallucinations increase with context length Bloated context = slower, more expensive calls LLM gets confused choosing between 50+ tool descriptions Result: Slow. Unreliable. Expensive agents. The "Slightly Smarter" Approach (Still Broken) RAG over tool descriptions. Seems reasonable: User query → embedding → top 5 matches → LLM picks Sounds clean. But embeddings can't distinguish intent. Similar words ≠ same meaning. Example: User says: "I need iPhone" Tool: check_product_catalog Embe