cowork-plugin-builder

name	cowork-plugin-builder
description	Interview the user step-by-step to gather every detail needed to build a Microsoft 365 Copilot Cowork plugin package (manifest.json + skills + optional MCP connectors), then produce a complete, self-contained build prompt the user can review or hand off for execution. Use when the user asks to "create a cowork plugin", "build a copilot plugin", "make a M365 copilot agent package", "package my skills as a plugin", "create a copilot agent with MCP", "build a plugin for copilot cowork", or "wizard me through a cowork plugin". Do NOT use for: creating a single personal skill (use the `skills` skill instead), installing an existing plugin, troubleshooting plugin uploads that already exist, or general M365 admin questions.
license	MIT

Cowork Plugin Builder

What This Skill Does

Guides the user through a relentless, wizard-style interview — one question at a time — to capture every detail needed to construct a Microsoft 365 Copilot Cowork plugin package. At the end, produces a fully-specified build prompt (matching the canonical schema and packaging rules) that the user can either review/copy or hand back to the assistant to execute.

When to Use

• "Help me build a Copilot Cowork plugin"
• "Create a M365 agent package with skills and an MCP server"
• "Wizard me through making a plugin"
• "Turn these skills into an uploadable plugin"
• "Package an MCP connector as a Cowork plugin"

When NOT to Use

• Creating a single personal skill that lives in OneDrive → use the skills skill
• The user just wants to install or upload an existing .zip → answer directly
• General questions about what Copilot Cowork is → answer directly
• Editing a plugin manifest the user has already drafted → edit it directly without the interview

Workflow

Phase 1: Set Expectations

Before asking anything, tell the user:

"I'll walk you through building a Copilot Cowork plugin one question at a time. I'll ask about the plugin's identity, each skill it should contain, and any MCP connectors. At the end I'll produce a complete build prompt you can review — and if you like it, I can build the package right away. Ready?"

Wait for confirmation, then proceed.

Phase 2: Interview — One Question at a Time

CRITICAL: Ask ONE question per turn. Never batch questions. Use AskUserQuestion with concrete option choices whenever a finite set fits; otherwise ask in plain prose. After each answer, record it in a running state summary (kept in your working memory, not shown to the user).

Ask in this order. Skip a section only if the user has already volunteered the answer earlier in the conversation.

Section A — Plugin Identity (5 questions)

1. Plugin short name — "What's the short display name? (max ~30 chars, e.g. 'Financial Research')"
2. Plugin full name — "And the full name? (e.g. 'Microsoft Financial Research Tools')"
3. Short description — "Give me a one-sentence description (under 80 chars) that shows in the agent list."
4. Full description — "Now a 2-4 sentence description for the agent details page."
5. Developer info — "Developer name, website URL, privacy URL, terms-of-use URL? (any defaults you want me to use for missing ones?)"

Section B — Branding (2 questions)

6. Accent color — "Hex accent color for the agent? (default #0078D4 Microsoft blue)"
7. Icon concept — "What simple glyph should the icons show? (e.g. 'chart', 'document', 'magnifier' — I'll generate 192×192 color and 32×32 outline PNGs)"

Section C — Language & Localization (1 question)

8. Default language and additional locales — AskUserQuestion (multiSelect):

   • Default language: en-US (US English), en-GB (UK English), it-IT (Italian), fr-FR (French), de-DE (German), es-ES (Spanish), ja-JP (Japanese), pt-BR (Portuguese), zh-CN (Simplified Chinese), Other
   • Additional locales: same list, allow multiple selections, or "None"

   The default language drives the defaultLanguageTag field in the manifest. Each additional locale gets a localizationInfo.additionalLanguages[] entry pointing at a localization/<tag>.json resource file the build prompt will scaffold.

Section D — Skills Inventory (loop)

9. How many skills? — "How many skills will this plugin contain?"

Then for each skill, ask in sequence (one question per turn):

a. Skill folder name — "Skill #N — kebab-case folder name? (e.g. 'company-snapshot')" b. Display name — "Display name shown in the UI?" c. Description (2-4 sentences) — "Short description of what this skill does." d. Trigger phrases — "Give me 3 trigger phrases a user would say to invoke it." e. Category — AskUserQuestion with options: productivity, communication, analysis, writing, research, finance, automation, custom f. Fluent UI icon — "PascalCase Fluent icon name? (e.g. BuildingBank, ChartMultiple, ShieldError)" g. Workflow steps — "Briefly: what are the steps the skill performs? (one line per step is fine)" h. Output format — "What does the skill produce? (email, report, summary, chart, etc.)" i. MCP tools used — "Which MCP tools does this skill call? (list tool names, or 'none' if pure prose-driven)"

Section E — MCP Connectors (loop)

10. Any MCP connectors? — AskUserQuestion: Yes / No
11. If yes: How many?

For each connector: a. Connector id — "Short id (lowercase, e.g. secedgar)?" b. Display name — "Display name?" c. Description — "What public data or tools does it expose?" d. MCP server URL — "Full URL of the remote MCP endpoint (e.g. https://example.com/mcp)?" e. Authorization — AskUserQuestion: None (public) / OAuth / API key / Other f. Valid domain — auto-extract hostname from URL, confirm with user

Section F — Wrap-up (2 questions)

12. Output paths — "Default output paths OK? output/<package-name>/ and output/<package-name>.zip — or override?"
13. Build now or just the prompt? — AskUserQuestion: "Generate the build prompt only" / "Generate the prompt AND build the package now"

Phase 3: Synthesize the Build Prompt

After the interview, write a markdown file at output/<package-name>-build-prompt.md containing a complete, self-contained build prompt that follows the canonical structure in references/build-prompt-template.md. Substitute every {{placeholder}} in the template with the collected answers. The output must include:

1. Goal — one paragraph stating what to build
2. Output Path — package folder + final ZIP path
3. Package Structure — tree showing every file (including any localization/<tag>.json files)
4. manifest.json (CANONICAL SHAPE) — full JSON with the user's collected values, including defaultLanguageTag and localizationInfo
5. Localization files — one JSON file per additional locale, with translated name.short, name.full, description.short, description.full
6. Schema Rules (CRITICAL) — encoded gotchas:
   • agentSkills and agentConnectors MUST be top-level (not under copilotAgents)
   • manifestVersion MUST be "devPreview"
   • packageName required (reverse-DNS)
   • $schema must be vDevPreview Teams URL
   • Fresh GUID v4 for id
   • validDomains must include MCP hostname
   • defaultLanguageTag MUST be a valid BCP-47 tag; locale files must match
7. SKILL.md Frontmatter spec — with cowork.category and cowork.icon nested under metadata:
8. The N Skills — one block per skill with folder, icon, triggers, MCP tools
9. Icons — 192×192 color PNG (#accent background, white glyph) + 32×32 outline PNG (transparent, white stroke); generate with Pillow
10. Packaging — Python zipfile snippet (manifest.json must be at ZIP root)
11. Validation Checklist — every gotcha as a checkbox
12. Upload Path — M365 Admin Center → Copilot → Agents → Upload agent. NOT Teams admin center.
13. Done When — explicit completion criteria

Phase 4: Present and Offer to Execute

Show the user:

• The path to the generated build prompt (output/<package-name>-build-prompt.md)
• A short summary: N skills, M MCP connectors, default language, K additional locales, output ZIP path
• The choice from Section F.13: if they said "build now", invoke the build steps in a fresh task; if "prompt only", stop and tell them they can paste the prompt to any session (including a fresh one) to execute it.

If building now, follow every step in the generated prompt verbatim and verify against the embedded checklist before declaring done.

Output Format

The primary deliverable is output/<package-name>-build-prompt.md — a single self-contained markdown file. If the user opted to build immediately, also produce output/<package-name>/ and output/<package-name>.zip per the prompt.

Guardrails

• One question at a time. Never batch. The interview style is the core value of this skill.
• Never fabricate developer URLs, MCP server URLs, or skill content. If the user doesn't know, mark with a clear [TODO: ...] placeholder in the build prompt.
• Always include the schema gotchas in the build prompt — they're encoded learnings from real upload failures.
• GUID v4 for id — generate fresh; never reuse an example GUID.
• Validate every MCP URL hostname lands in validDomains.
• BCP-47 tags — validate language tags (e.g. en-US, it-IT); reject invalid ones.
• Confirm before building — even if the user said "build now" upfront, show the assembled manifest snippet before zipping.

Key Learnings Encoded

This skill bakes in the lessons from real plugin upload failures:

1. Schema shape: agentSkills / agentConnectors are top-level — nesting them under copilotAgents fails strict M365 validation.
2. Two upload surfaces: Teams admin center accepts the same package but silently drops unknown root properties. Always upload via M365 Admin Center → Copilot → Agents.
3. Frontmatter nesting: cowork.category and cowork.icon go UNDER metadata:, not at the top of the YAML.
4. packageName required: Reverse-DNS, e.g. com.contoso.financial-research.
5. Rebuild the ZIP every time: Stale ZIPs use old content.
6. manifest.json at ZIP root, not in a subfolder.
7. Localization: defaultLanguageTag plus localizationInfo.additionalLanguages[] pointing at localization/<tag>.json resource files.