How you tell an agent what to do

Two things you give an agent

You steer an agent with two inputs, and it helps to keep them separate.

• The instructions (the standing brief). Often called the prompt or system prompt, these set who the agent is, how it should behave, and what it may and may not do. They persist across the task, like a job description.
• The goal (what "done" means). This is the specific objective for the task in front of it right now — the outcome that says the work is finished.

An agent follows the brief, not your intent

Here is the executive's mental model, and the one place people are surprised: an agent does what its instructions actually say, not what you meant. It has no access to the intent in your head — only the words you gave it.

Two consequences follow directly:

• A vague goal produces vague action. "Look into our exposure" invites a vague answer; "list every position over $1M and flag the three largest by risk" gets a precise one.
• An unstated constraint is an unenforced one. If a boundary matters — a budget, a system it must not touch, an approval it must wait for — it has to be written down. Unsaid is unbounded.

The right instinct is to treat it like briefing a new hire on day one. You would not hand a capable stranger a one-word task and hope; you would state the objective, the bounds, and what a good result looks like. Clear direction beats clever phrasing every time.

See it in kestrel

Kestrel makes the brief and the goal explicit and bounded — the agent's authority and objective are written down, not assumed. Watch one run against a generic instrument, no signup, no card:

npx kestrel.markets sim fomc-rate-decision-whipsaw

It prints a certified proof URL you can recompute yourself. Drop the kestrel.markets MCP server into your client and the setup carries to the next session — no account in between.