Agent Instruction Block Design Guide
Write agent instructions that behave. The fiftieth user gets the same result you did on day one.
Extracted from an open-source Copilot Chat agent library, now 82 published.
The free, open-source Copilot prompt library that sits under this work was cited by Jared Spataro (Microsoft, AI at Work) in his 25 February 2026 note. He was citing that free repo when it held 300+ prompts. This is a separate, paid product and he did not review or endorse it.
The situation
Anyone can paste an instruction block into Copilot Studio. What separates agents that get used from agents abandoned after a week is the design.
Most instruction blocks fail not because they are wrong about what the agent should do, but because they are silent about what it should never do. They are vague about edge cases. They say "be helpful" instead of naming the exact action that would be unhelpful.
What this is
Twelve design patterns extracted from building real Copilot Chat agents, open source and in production, a library that now runs to 82 published agents. Each pattern includes a before and after instruction block and a plain explanation of which failure mode it prevents.
What is inside
- 12 design patterns with before and after examples
- The failure mode each pattern prevents
- A review checklist for somebody else's instruction block
The problem: Agents that begin every response with filler phrases regardless of content, tone, or urgency.
BEFORE Respond professionally and helpfully. Avoid being too casual.
AFTER Do not open with: "I hope this finds you well", "I wanted to reach out", "Great question!", "Absolutely!", "Certainly!", "Of course!", "Happy to help", "I'll be happy to assist you with that", or any filler warm-up phrase. Begin with the substance of the response. No banned vocabulary: pivotal, robust (abstract), vibrant, seamless, impactful, groundbreaking, revolutionary, game-changing.
Each pattern also names the failure modes it prevents, and some prevent several. This one prevents The Opener Addict.
Who it is for
- Anyone writing instruction blocks for Copilot Studio or Copilot Chat agents
- Reviewers who have to judge whether somebody else's agent is safe to ship
Who it is not for
- People who want finished agents rather than the patterns behind them. That is the Agent Pack.
Questions people actually ask
Does this work if we are on E3 rather than E5?
Yes. M365 Copilot is a paid add-on that sits on top of a qualifying M365 licence, so the licence tier underneath changes what data Copilot can reach, not whether this material applies. Where an E5-only control is the cleanest answer to something, the material says so and gives the E3 route as well.
Is this current for the June 2026 GA wave?
Yes. Cowork went generally available worldwide on 16 June 2026 and brought a metered layer billed in Copilot Credits at $0.01 each. Everything here is written against that change rather than around it. When a document is revised, Gumroad re-delivers it to everyone who already bought, free.
What if we have not enabled Cowork yet?
That is the common case and it is fine. The metered layer is additive and off by default until an admin enables it, so your bill today is still flat seats. Reading this before you switch it on is the cheaper order to do it in, because the decisions get harder to reverse once makers start building.
Do the patterns only apply to Microsoft agents?
They were extracted from Copilot work and the examples are Copilot-shaped, but the failure modes are not vendor-specific. The pattern that stops an agent answering outside its scope reads the same whichever platform you are on.
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Subject: Approval request: Agent Instruction Block Design Guide ($19, one-time) Hi [Manager], I would like to expense a one-time $19 purchase: Agent Instruction Block Design Guide by Kesslernity. What it is: Write agent instructions that behave. The fiftieth user gets the same result you did on day one. What we get: - 12 design patterns with before and after examples - The failure mode each pattern prevents - A review checklist for somebody else's instruction block Why it is worth it: it is a one-time purchase with no subscription, and at $19 there is no statement of work, no discovery call and nothing to negotiate. The author publishes the open-source Copilot prompt library that Microsoft's CMO for AI at Work cited as "battle-tested in production environments". A downloadable invoice is available from the purchase receipt for expenses. [Your name]
Agent Instruction Block Design Guide
Write agent instructions that behave. The fiftieth user gets the same result you did on day one.
Get it for $19Licensed, not sold. The full License & Terms apply. Kesslernity is an independent publisher: this is independent analysis, not affiliated with, sponsored by, or endorsed by Microsoft. It is practitioner guidance, not professional, legal, or financial advice.
What this pairs with
Picked by hand, not by sales data.
Copilot Agent Pack, Vol. 1
Six governed Copilot Studio agents, finished for governance rather than for a demo.
$49→Naming the Swarm
A governance-first naming convention for your fleet of M365 Copilot agents.
$39→Agent Instruction Block Design Guide is also part of From Decision to Deployment: $39 for both instead of $48 separately.