create-cowork-skill

name	create-cowork-skill
description	Authors a Microsoft 365 Copilot Cowork custom skill (a SKILL.md plus its companion files) that Cowork reliably discovers and runs. Covers the frontmatter contract, the kebab-case name-matches-folder rule, OneDrive placement, companion-file limits, and the run-and-tune loop that makes a skill trigger on natural phrasing. Use when asked to create a cowork skill, author a custom skill for Cowork, write a SKILL.md for Copilot, build a Copilot Cowork skill, package a skill for upload, or fix a Cowork skill that will not load or will not trigger.
metadata	{"version":"1.0.0"}

Create a Cowork Skill

Author a Microsoft 365 Copilot Cowork custom skill: a SKILL.md file with YAML frontmatter and plain-language instructions, plus any companion files it needs.

A Cowork skill is not code. It is a recipe written for a capable colleague who has your permissions and none of your context. The two things that decide whether it works are the description (does Cowork reach for it at the right moment) and the specificity of the body (does it produce your format rather than a generic one).

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The minimum viable skill

---
name: weekly-report
description: Generates my Northern Europe weekly status report from my sent emails, meetings, and latest figures. Use when I say write my weekly report, status update, or ask for the week's summary.
---

Gather my sent emails and calendar events from the past seven days.

Fill every section in order:
- Highlights: three to five outcome-led wins.
- Risks: anything slipping, with the owner named.
- Next week: the three commitments I am making.

Save the finished report as a Word document titled with the week ending date.

Two required frontmatter fields, name and description. Nothing else is required.

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Hard rules (these are what break skills)

• name is kebab-case and must match the folder name exactly. skills/weekly-report/SKILL.md carries name: weekly-report. A mismatch is the single most common cause of a skill failing to load. Lowercase alphanumerics and hyphens only; no consecutive, leading, or trailing hyphens.
• The manifest filename is exactly SKILL.md, uppercase.
• The description is the only thing loaded until the skill triggers. If it does not name the situation and the trigger phrases, the skill never runs no matter how good the body is.
• Discovery happens at the start of a session. A skill you just saved appears in the next new task, not the one already open. Always test in a fresh session.
• Never invent a capability in the body. The skill inherits the user's permissions and Cowork's built-in skills; it cannot reach systems Cowork cannot reach.

Microsoft's own docs are inconsistent here: the OneDrive authoring page shows name: Weekly Report (title case with a space), while the plugin-development page specifies kebab-case matching the folder and lists it as an Error-severity validation rule. Follow the strict rule; it satisfies both.

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Where the skill lives

Goal	Location
Personal skill, authored by hand	OneDrive Documents/Cowork/skills/<name>/SKILL.md
Authored conversationally	Ask Cowork in chat to build a skill, or use Customize > Skills > Add > Create new
Import an existing skill	Customize > Skills > Add > Upload skill (.md, .zip, or .skill)
Share with the organization	Package as a plugin and publish, see the plugin path in references/format-reference.md

Create the Documents/Cowork/skills/ folder if it does not exist. Each skill gets its own subfolder named for the skill.

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Workflow

1. Name the recurring job. A skill is worth authoring when you have re-explained the same format more than twice. If the task happens once, just ask for it.
2. Find the house format. Locate the template, the past example, or the document the output must match. This becomes a companion file, not a paraphrase in the body.
3. Write the description first. Say what it produces and when to use it, including the phrases you would actually type. See references/authoring-and-tuning.md.
4. Write the body as an ordered recipe. Sources to gather, sections to fill in order, rules for judgement calls, and the artifact to save.
5. Save into its own folder with the companion files beside it.
6. Test in a new session, by name first, then without naming it.
7. Tune what failed. Ask Cowork which phrasings would miss the skill and which instruction let a weak result through, then fold the answers back in.

Steps 6 and 7 are not optional polish; a skill that has never been run and corrected is a draft.

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Reference material

Read the reference file that matches the task:

• references/format-reference.md — the full frontmatter contract, size and count limits, companion-file rules and validation table, the three-layer loading model, and cross-platform compatibility with Claude Code and other Agent Skills hosts.
• references/authoring-and-tuning.md — how to write a description that triggers, how to structure the instruction body, evidence and refusal rules, and the run-and-pressure-test loop.

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Quality bar

A skill is done when all of these hold:

• It triggers in a new session from phrasing that does not name it.
• Its output matches the house format without follow-up correction.
• It refuses or asks rather than inventing anything it cannot source.
• Its companion files are referenced by name in the body, so Cowork knows to open them.