How are you handling authorization for AI agent tool calls in production?

We've been building invisibleact.com - agents that call external tools (APIs, databases, payment systems) and keep running into the same problem: Schema validation passes. Identity checks pass. Permissions are valid. And the action is still wrong — because the context changed, or the agent inferred something it shouldn't have. Curious how others are solving this: · Are you validating at the tool level, or before it? · How do you handle multi-turn drift where the agent slowly goes off-mission? · Any patterns for delegating authority to sub-agents without leaking root credentials? Not looking for tool recommendations — more interested in architectural patterns people are actually using.