The deep view
On typing, regression, and the audit trail.
The point of Prompt Engineer is the typing. A prompt is not a string in a config file. A prompt is a typed artifact with an input schema, an output schema, tool calls, and fallbacks. The contract is the contract. The agent writes the prompt, the contract, and the test set at the same time. The diff is in the repo. The reviewer agent reads the diff before the prompt is allowed to ship.
The regression tests are the safety net. The agent writes a test set, the test set is committed, the test set runs on every change. The eval harness reads the result. Pairwise comparison, single-rating, golden set — the operator picks the harness, the agent runs it on a schedule. The weekly eval summary lands in the inbox. The reviewer agent flags the regressions before the prompt is allowed to ship.
The MCP contract is the integration story. Every tool call is typed, every input is validated, every output is parsed, every call is logged. The contract drift is caught by the reviewer agent before the prompt is allowed to call the tool. The multi-model routing is on by default — the operator can route the same prompt across two models, read the diff, ship the better one. The routing decision is recorded in the prompt log.
The audit trail is the prompt log in the repo. Every change, every test, every eval, every routing decision. Not in a vendor dashboard, not in a Slack channel, not in an email thread. The audit trail of the prompt is the prompt. The operator can read it, version it, branch it, hand it to another team. The prompt is a real artifact with a real history.