“It’s the Architecture, Stupid” — Why Prompt Engineering Won’t Fix Agents

I think this is exactly the right addition.

“Ask if unsure” should not be a sentence inside the prompt. It should be a runtime state. If a skill is missing required inputs, execution should be blocked and the system should enter clarification instead of silently filling the gaps.

I would generalize this as method validity gating: before a model or skill is allowed to execute, the architecture should check whether the required epistemic conditions are met.

For example:

• arithmetic should be routed to a deterministic calculator once the operation is identified
• retrieval should be mandatory when current or source-bound knowledge is required
• graph-based answers should depend on the declared graph structure
• missing required inputs should trigger clarification, not inference

I have been experimenting with this idea in a small DESi router prototype: task → validity check → appropriate method → structured execution → auditable result.

So the deeper shift is not only from Prompt → Model → Output to Skill → Execution → Structured Output, but also toward procedural control over when an answer is allowed to exist.

DESi outline:

hstre.github.io

DESi — Deterministic governance for LLM pipelines

Replay-stable. Read-only. Auditable. DESi watches LLM pipelines from the outside — and reports its own failures too.