You have typed the same instructions into Copilot enough times to recite them. Nobody told you there is a place to put them.
That place is a skill. But before you can use one, you need to know what it actually is, because “skill” has quietly become one of the most overloaded words in the Copilot vocabulary. Microsoft uses it for a specific feature in Excel and PowerPoint. It uses it again, with a different packaging mechanism, in SharePoint and in Agent Builder. And in Word and OneNote, “skill” doesn’t exist yet as a discrete feature — which is its own kind of useful answer. If you only half-know which one someone means, every conversation about “adding a skill” turns into a guessing game.
Why It Matters
Repetition is a signal, not just an annoyance. If you are retyping the same instructions into Copilot every week, that is a sign the instructions are stable enough to save, not just a sign that Copilot has a bad memory. Knowing where “stable enough to save” actually lives in Microsoft 365 changes what you build first: a five-minute skill upload, or a bigger project you didn’t need yet.
What You’ll Learn
- The three-tier distinction: prompt, skill, agent
- Which Microsoft 365 apps have a documented Skills feature, and which don’t
- How the packaging differs from one surface to the next
- How to decide which tier a repeated task actually belongs in
The Three Tiers
A prompt is a one-time instruction. It disappears once Copilot answers and you close the chat. You bear the full cost of re-explaining it every time.
A skill is a reusable instruction file Copilot can pick up when the task calls for it, instead of you retyping the same guidance each time. Microsoft’s own definition, used consistently across its Copilot in Excel and Copilot in PowerPoint support documentation, describes skills as reusable, instruction-based capabilities that give Copilot domain expertise, workflows, and task-specific guidance for repeatable work.
An agent is a packaged assistant built for a defined purpose, with its own name, knowledge sources, and audience. An agent can carry skills inside it, but it is a bigger commitment than either a prompt or a skill: someone has to own it, scope its knowledge, and decide who gets to use it.
Each tier solves a repetition problem one level up. A skill formalizes a prompt you kept rewriting. An agent formalizes a set of skills and knowledge sources you kept invoking by hand.
Where This Actually Lives Today
This is the part that usually gets skipped, and it’s the part that matters. “Skill” is not a metaphor here — it names real, current features, and the boundaries between them are specific enough to save you an argument.
- Copilot in Excel — A skill is a folder containing a
SKILL.mdfile, uploaded to OneDrive. It shows up in the Copilot pane’s skills menu, and you invoke it either by picking it from that menu or typing an @mention, like@data-analysis. - Copilot in PowerPoint — Same
SKILL.mdmodel, plus a OneDrive-based custom-skill upload flow you manage from the Copilot pane’s skills menu. - Copilot in Word and Copilot in OneNote — No dedicated Skills feature exists in either app today. If someone tells you they built a “Word skill” and invoked it with an @mention, ask what they actually did — Word doesn’t expose that picker.
- Copilot in SharePoint — Skills are a native capability of Copilot in SharePoint, which is itself in preview. They’re stored as Markdown files in a site’s Agent Assets library, at a path like
/Agent Assets/Skills/<skill-name>/SKILL.md, and can be created directly through chat or edited as a file. There are no separate admin controls to turn skills on or off: by default, anyone with Edit permissions on the site can create one and anyone with View permissions can run it. A SharePoint skill is scoped to what the user already has permission to do; it can’t call external systems or execute custom code. - Agent Builder — The Configure tab has its own Skills section, in preview, with a different packaging mechanism than the app-level skills above: a skill here is a
.zipfile containing aSKILL.mdmanifest and optional resource files or scripts, uploaded directly into the agent (up to eight skills per agent, 50 MB per package). Note the availability constraint: custom skills in declarative agents are in preview for organizations enrolled in the Microsoft Frontier Program, so this one may simply not be present in your tenant.
Same underlying idea — a name, a description, and instructions Copilot loads when it’s relevant — but the packaging and the invocation method both change depending on which surface you’re in. Check the specific app or builder in front of you before assuming a skill you built in one place will look or work the same way in another.
Practical Scenarios
Excel. Say you clean and reformat the same kind of weekly sales export before you’ll trust any analysis on it: strip blank rows, standardize date formats, flag duplicates. That’s a prompt doing a skill’s job. Upload that cleanup routine as a SKILL.md file to your Copilot in Excel skills folder, and it becomes something you invoke with @cleanup instead of re-explaining it on every new workbook.
PowerPoint. Say every deck you build needs to follow the same title-slide layout, font pairing, and citation footer before you’ll present it. Instead of describing that formatting in every prompt, upload it as a custom skill in Copilot in PowerPoint. From then on, you (or anyone you share the skill with) can invoke it by name and get a deck that already matches house style.
SharePoint. Say your team reviews vendor contracts on a shared SharePoint site, and every time someone asks Copilot in SharePoint to check a new contract, they retype the same six-question checklist first. Ask Copilot in SharePoint, in chat, to save that checklist as a skill. It lands in the site’s Agent Assets library, and from then on, anyone with access to that site can invoke it by name instead of retyping it.
Now say one of these checklists needs to run as part of a larger intake process that also has to log results and notify a reviewer. That’s no longer a single-surface skill problem. That’s an agent problem.
Best Practices and Common Pitfalls
Don’t build an agent to solve a problem a skill already solves at a fraction of the overhead.
Don’t assume “we don’t have Skills working” means the same thing across every app. Check which surface you’re actually in before you diagnose anything as broken. A missing Skills picker in Word isn’t a bug; it’s the current state of that app. And a missing Skills section in Agent Builder may mean your tenant isn’t in the preview program that gates it, not that something is misconfigured.
Don’t assume a skill built in one surface transfers to another. The packaging differs — a OneDrive folder in Excel and PowerPoint, an Agent Assets library entry in SharePoint, a .zip upload in Agent Builder — so a skill built for one isn’t automatically usable in another.
Do treat a skill’s output the way you’d treat any Copilot draft: it’s a starting point that still needs your review, not a finished answer just because it came from something you built.
Key Takeaways
The prompt-skill-agent split is not an abstract framework. It maps to specific features that exist in some Microsoft 365 apps and not others: Skills in Copilot for Excel and PowerPoint, and Skills in preview for Copilot in SharePoint and Agent Builder — each with its own packaging, its own invocation method, and in Agent Builder’s case its own preview-program requirement. Word and OneNote don’t have a documented Skills feature yet. Knowing which of these you’re actually being asked about saves you from building the wrong thing, or from arguing past someone who means something different by the same word.
Try This Today
Find one prompt you’ve retyped into Copilot at least three times this month. If it’s tied to one file in Excel or PowerPoint, that’s a personal app skill. If it’s a checklist your whole SharePoint site keeps reusing, ask Copilot in SharePoint to save it as a skill from chat. If you’re already building in Agent Builder, check the Skills section on the Configure tab before you write another paragraph of instructions to cover a case a packaged skill could handle. If it’s something a whole team keeps invoking by hand across different tools, that’s a sign you’re looking at agent territory, not a personal skill.
Additional Resources
- Microsoft Support: Use skills with Copilot in Excel to complete repeatable tasks
- Microsoft Support: Use custom skills with Copilot in PowerPoint
- Microsoft Learn: Extend Copilot in SharePoint with skills
- Microsoft Learn: Custom skills in declarative agents (preview)
- Microsoft Learn: Add custom skills to your declarative agent in Agent Builder (preview)
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