# Brendan Cody-Kenny: APIs now encode the laws of physics for AI agents: the legal state transitions, not just the available functions.

Technical Due Diligence for Software M&A https://sub.xiliary.com/p/brendancodykenny

### 2026-10-06 reading #agents #api-design #erp #mcp #state-machines
APIs now encode the laws of physics for AI agents: the legal state transitions, not just the available functions.
- The UI used to constrain the state machine. Onboarding showed one screen, a small set of legal moves, then the next. Invalid transitions simply weren't rendered.
- Take the UI away and those guardrails have to move into the API: given the current state, what can happen next, what is invalid, and what information is missing?
- An agent-native API is therefore partly API, partly state machine, partly onboarding flow. It makes the legal moves legible to the agent.
- That matters enormously for CRM and financial systems, where agents need safe state changes rather than arbitrary function calls.
- ERP is the harder version: the data model is manageable, but business rules, approvals and industry-specific workflows make the state machine much richer.

https://sub.xiliary.com/p/brendancodykenny/posts/53/apis-now-encode-the-laws-of-physics-for-ai-agents-the-legal