44 lines
2.3 KiB
Markdown
44 lines
2.3 KiB
Markdown
# Agent system-prompt best practices (2026)
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Synthesised from current (2026) prompt-engineering guidance. These are the rules
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the **agent-creator** meta-prompt enforces when it drafts a new agent, and the
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checklist to apply when writing any agent here.
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## Core philosophy
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- **It's information architecture, not magic words.** Better context beats
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longer prompts. Engineer *what the model knows and when*, not verbosity.
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- **A system prompt is operational policy, not a script.** Define the agent's
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identity, job, scope boundaries, success criteria, and stop/escalate rules —
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not rigid step-by-step instructions (the model runs many turns/tools).
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## Structure (in this order)
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1. **Identity & job** — what the agent *is*, its single job, and explicitly
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*where the job begins and ends*.
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2. **Operating rules** — tone, language, output format constraints, length.
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3. **Tools** — which MCP tools it has, **when and why** to use each, and when
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*not* to. Models under-use tools unless told explicitly.
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4. **Procedure** — the ordered steps/sections to produce (use a numbered list).
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5. **Boundaries & failure** — permission limits, what to never do, and graceful
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degradation ("if a tool fails, write '(nicht verfügbar)' and continue —
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never invent values").
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6. **Closing actions** — side effects (notify, log) stated explicitly.
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## Mechanics
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- **Explicit delimiters.** Separate *rules* from *content the model processes*
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with stable markers (XML-ish tags or clear headers). Most failures come from
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the model conflating instructions with data.
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- **No assumed state.** Dynamic facts (date/time, sensor values) must come from
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a tool call, never the model's prior. State this in the prompt.
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- **Determinism aids.** Give concrete IDs/keys; constrain output shape; show one
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short example only when tone/format matters.
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- **Escalation/stop conditions.** Say when to stop, when to ask, when to bail.
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- **Idempotency/self-logging** where relevant (e.g. an agent that logs its own
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output so a later run can find it).
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## Anti-patterns
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- Walls of prose; mixing rules and data; "be helpful/creative" with no scope;
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assuming the current date; vague tool guidance; no failure path.
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The Morning Briefing agent (`morning-briefing-agent.md`) is the worked example
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that follows all of the above.
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