Feat/improved subagent support

[agreaves-ms]

Pull Request

Description

Adds support for subagent declarations in custom agent files.

• Copilot will eventually support agents: in custom agent files, enabling consistent subagent behavior and reuse across agents
• Adds #tool: support for referencing tool names within agent files
• These features are not yet implemented in GitHub Copilot; further work will continue when support ships

Related Issue(s)

Type of Change

Select all that apply:

Code & Documentation:

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update

Infrastructure & Configuration:

• GitHub Actions workflow
• Linting configuration (markdown, PowerShell, etc.)
• Security configuration
• DevContainer configuration
• Dependency update

AI Artifacts:

• Reviewed contribution with prompt-builder agent and addressed all feedback
• Copilot instructions (.github/instructions/*.instructions.md)
• Copilot prompt (.github/prompts/*.prompt.md)
• Copilot agent (.github/agents/*.agent.md)
• Copilot skill (.github/skills/*/SKILL.md)

Other:

• Script/automation (.ps1, .sh, .py)
• Other (please describe):

Testing

Checklist

Required Checks

• Documentation is updated (if applicable)
• Files follow existing naming conventions
• Changes are backwards compatible (if applicable)
• Tests added for new functionality (if applicable)

Required Automated Checks

The following validation commands must pass before merging:

• Markdown linting: npm run lint:md
• Spell checking: npm run spell-check
• Frontmatter validation: npm run lint:frontmatter
• Skill structure validation: npm run validate:skills
• Link validation: npm run lint:md-links
• PowerShell analysis: npm run lint:ps

Security Considerations

• This PR does not contain any sensitive or NDA information
• Any new dependencies have been reviewed for security issues
• Security-related scripts follow the principle of least privilege

Additional Notes

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.22%. Comparing base (8133b36) to head (16483c9).

Additional details and impacted files

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  Coverage   76.22%   76.22%           
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  Files          20       20           
  Lines        3503     3503           
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  Hits         2670     2670           
  Misses        833      833           

Flag	Coverage Δ
pester	76.22% <ø> (ø)

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see 1 file with indirect coverage changes

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[Copilot]

Pull request overview

This PR updates the repo’s prompt/agent authoring guidance and artifacts to prepare for improved subagent orchestration (executor/evaluator/updater pattern) and tool referencing, plus expands the workspace MCP server configuration.

Changes:

• Expands .vscode/mcp.json with additional MCP servers and ADO-related inputs.
• Simplifies several prompt files to delegate more behavior to the prompt-builder agent and introduces new “leaf” subagent agent files.
• Updates prompt-builder.instructions.md and the prompt-builder / task-planner agents to reflect the new subagent model and streamlined protocols.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
.vscode/mcp.json	Adds MCP inputs/servers, but currently introduces JSON validity issues and an incomplete server definition
.github/prompts/task-plan.prompt.md	Adds argument hint and tweaks planning step flow
.github/prompts/prompt-refactor.prompt.md	Refactors prompt to be more mode-driven, but has input/argument hint mismatch
.github/prompts/prompt-build.prompt.md	Refactors prompt to be more mode-driven, but has input/argument hint mismatch
.github/prompts/prompt-analyze.prompt.md	Simplifies analysis prompt and delegates to prompt-builder agent
.github/instructions/prompt-builder.instructions.md	Updates authoring standards and documents new agent frontmatter fields (currently out of sync with schema)
.github/agents/task-planner.agent.md	Updates wording, adds clearer phase transitions, compresses template guidance
.github/agents/prompt-builder.agent.md	Introduces orchestrator-style agent with subagent list (currently schema-incompatible)
.github/agents/prompt-builder-updater.agent.md	Adds updater “leaf” agent (currently schema-incompatible frontmatter)
.github/agents/prompt-builder-executor.agent.md	Adds executor “leaf” agent (currently schema-incompatible frontmatter)
.github/agents/prompt-builder-evaluator.agent.md	Adds evaluator “leaf” agent (currently schema-incompatible frontmatter)

[WilliamBerryiii]

Thank you for your contribution, @agreaves-ms. We restructured the PR description to follow the project's pull request template. Please review the updated description and check any additional boxes that apply to your changes.