Building LLM-Backed Features

Calling a model is easy; shipping a feature around one is where the bugs live. The model is a non-deterministic dependency whose inputs are spread across your codebase and whose outputs get presented to users as facts. This skill covers the failure modes that recur in that gap. (Building a server that exposes tools to a model is the other direction — see ../mcp-servers/SKILL.md.)

Every string the model reads is prompt surface

Wording that shapes model behavior does not live only in the prompt template. It typically lives in four places that drift apart independently: