To strike the right balance, I’d focus on modular, well-documented tools with strict access control. Each callable function should have:

1. Clear purpose & description – so the LLM knows when to invoke it.

2. Input/output validation – prevents unintended actions or SQL injection.

3. Sandboxing & logging – safely test new tools and track all actions for observability.

4. Chaining rules – allow sequences of safe function calls without breaking autonomy.

5. Error handling & fallback paths – ensures recovery if a step fails.

Essentially: flexible enough for agent creativity, but safe enough to prevent misuse.

For complex workflows, I’d also use a tool registry with versioning and permissions, so the agent only accesses approved functions.