Copilot Cowork Skills: A Practical Guide

Copilot Cowork skills are saved instructions, written in a SKILL.md file, that tell Cowork how to do a specific job. You can create one on the Customize page, ask Cowork to build one in chat, or add the file to a folder in your OneDrive. Cowork checks each skill's quality automatically, and you can share a skill with specific people in your organisation.

Cowork already has built-in skills for everyday work, including Word, Excel, PowerPoint, PDF, email, scheduling, meetings, daily briefings, enterprise search and deep research. When Cowork loads a skill during a session, it shows up in the side panel (Microsoft: Use Copilot Cowork).

Custom skills add your own methods. Think of a new starter who knows how to use Word and Outlook but doesn't know how your team writes a steering group update. The custom skill is their job card: the steps, the format, the checks and where to find the template.

A Cowork skill is a SKILL.md file with the same basic layout as the open Agent Skills standard: a short header with a name and a description, followed by instructions in Markdown. See What Are Agent Skills? for the standard.

All of the following comes from Microsoft's current Cowork documentation (Microsoft: Use Copilot Cowork):

• Create on the Customize page. Open Customize, select the Skills tab, then Add > Create new. Cowork walks you through the name, description, category and instructions, and drafts the SKILL.md file.
• Create in chat. Tell Cowork you'd like help creating a skill and it follows the same steps.
• Create in OneDrive. Add a folder for the skill under /Documents/Cowork/skills/ with a SKILL.md file inside. Cowork finds custom skills at the start of each session.
• Upload a skill. On the Skills tab, select the arrow next to Add, then Upload skill, and choose a .md, .zip or .skill file that includes a name and description. Microsoft advises uploading only skills from sources you trust.
• Share a skill. Open the skill's detail page, select Share, then choose specific users in your organisation. When you change a shared skill, select Re-share to update everyone.
• Limits. Up to 50 custom skills, each SKILL.md up to 1 MB, and up to 20 companion files totalling 10 MB per skill. Custom skills aren't supported in Cowork on mobile.

Cowork also evaluates a skill whenever you create or update it. It scores the skill out of 100 across four areas: trigger clarity, instruction specificity, scope boundaries and robustness. It also flags common faults, such as a description that's too broad, has no trigger phrases or runs past the character limit.

Copilot Studio is different. Copilot Studio skills are for agents you build in Copilot Studio, not for your own Cowork sessions. You add them to an agent by uploading a SKILL.md or ZIP file, writing one from blank or generating one with AI (Microsoft: Skills overview for Copilot Studio agents).

Westbay Civil, a fictional engineering firm, sends a weekly update to each project's steering group. Project managers pull it together from emails, Teams chats and site reports, and the results vary.

Their Cowork skill:

• Name: Steering Group Update
• Description: Prepares the weekly steering group update from this week's project emails, Teams messages and site reports. Use when asked for a steering update, weekly project report or board status note.
• Inputs: the project name, this week's site reports from SharePoint and last week's update.
• Steps: summarise progress against milestones, list decisions needed, list risks with owners, and note any change to the budget or programme.
• Decisions: if a milestone moved and the sources don't say why, list the question rather than writing an explanation.
• Output: a Word document using the steering update template, saved to the project's SharePoint folder.
• Stop point: save the draft for the project manager. Don't email the steering group.

Cowork asks for approval before sensitive actions such as sending an email, which gives a natural review point. Even so, write the stop point into the skill so the boundary doesn't depend on a setting.

• Choose one job you repeat weekly, with a result you can check.
• Write down the inputs, the output sections and the stop point.
• In Cowork, open Customize > Skills and select Add > Create new.
• Answer the guided questions for name, description, category and instructions.
• Read the quality report and fix the top issues it lists.
• Run the skill on a real project and compare the draft with the sources.
• Run the three tests below, then share it with one colleague.

• A normal week. Give it a full week of material. Check each decision and risk against the original emails and reports.
• Incomplete input. Remove the site report. The update should say the report is missing, not describe site progress from memory.
• An unrelated request. Ask for a client newsletter. The steering update skill shouldn't load. If it does, narrow the description.

Keep these cases. Cowork's automatic evaluation is useful, but your own examples show whether the skill works for your projects.

Cowork's sharing works within Microsoft 365. Many teams also use Claude or ChatGPT, and each tool ends up with its own copy of the same skill. A skill tells your AI what to do. Your knowledge base shows it how, in detail. Your company context tells it who it's for. The Contexta harness brings them together, in every AI.

Contexta holds your skills with your company context: your terminology, naming and formats, set for the company and adjusted for each team. Your knowledge base stays where Microsoft 365 teams already keep it, in SharePoint, and skills point to it there. Company, team and personal spaces give each team its own home and rules, and version history lets you compare and restore.

We haven't yet tested a Contexta connection with Microsoft 365 Copilot Cowork end to end, so this guide covers Cowork's own skill features only. Check Integrations for supported setups, and see Product for how Contexta works with the tools it supports.