Add applicators to aspire mcp init for agent instructions and Playwright MCP server configuration

[Copilot]

Description

Extends aspire mcp init with an applicator-based approach for configuring agent environments. Users are presented with a list of available applicators and can select which configurations to apply.

Changes

Applicator-Based Configuration

• Removed prompts in favor of applicators that users can individually select
• Each detected agent environment offers up to 3 applicators:
  • Configure Aspire MCP server (if not already configured)
  • Configure Playwright MCP server (if not already configured, offered even when Aspire MCP exists)
  • Create agent instructions file (offered once across all scanners, only when AGENTS.md doesn't exist)

Context Extension

• AgentEnvironmentScanContext includes:
  • AgentInstructionsApplicatorAdded - flag to ensure agent instructions applicator is added only once across all scanners

API Refactoring

• IAgentEnvironmentDetector.DetectAsync() signature simplified to accept AgentEnvironmentScanContext and CancellationToken (2 parameters instead of 5)
• Context construction moved from AgentEnvironmentDetector to McpInitCommand for better separation of concerns

Scanner Behavior

• All four scanners (VS Code, Claude Code, OpenCode, Copilot CLI) add separate applicators for:
  • Aspire MCP server configuration (only if not already configured)
  • Playwright MCP server configuration (npx -y @playwright/mcp@latest) (only if not already configured)
  • Agent instructions file creation (via CommonAgentApplicators.TryAddAgentInstructionsApplicator)
• Each applicator checks configuration state independently
• Scanners are focused on MCP configuration, with agent instructions handled centrally

Agent Instructions

• Centralized instruction file creation in CommonAgentApplicators helper class
• Creates AGENTS.md at workspace root only if it doesn't already exist
• Simple file existence check:
  • If AGENTS.md exists, no applicator is offered (regardless of content)
  • If AGENTS.md doesn't exist, offers to create it
  • Only creates AGENTS.md (no fallback to alternative filenames)
• Single file standard across all agent environments
• Applicator added only once via context flag

Example Output
When Aspire and Playwright applicators are selected for VS Code, mcp.json includes:

{
  "servers": {
    "aspire": {
      "type": "stdio",
      "command": "aspire",
      "args": ["mcp", "start"]
    },
    "playwright": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@playwright/mcp@latest"]
    }
  }
}

When the agent instructions applicator is selected, a file is created at the workspace root as AGENTS.md:

# Copilot instructions

This repository is set up to use Aspire. Aspire is an orchestrator for the entire application and will take care of configuring dependencies, building, and running the application. The resources that make up the application are defined in `apphost.cs` including application code and external dependencies.

...

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
  • No
• Does the change require an update in our Aspire docs?
  • Yes
  • No

Original prompt

Add a prompt to the aspire mcp init that prompts whether the command should add agent environment specific instructions files based on the selected agent environments.

This selection will need to be passed into the the applicator as a context object with this option selected. If the context object has a flag that says that they do want the agent instructions created then applicators that support dropping agent instructions can create the files.

Also add a prompt to ask whether they want to pre-configure playwright MCP server (this should be added to the context as well).

Here is an example of the agent instructions that we should use. For the actual content of the agent instructions - for now just create a placeholder resource.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 13375

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 13375"

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 13375

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 13375"

[mitchdenny]

@copilot lift the instructions generation logic out of the scanners (and remove the flag from the scanner context). It looks like AGENTS.md file is pretty much the standard across most environments. If the AGENTS.md file does not exist create it, if it does exist create AGENTS.aspire.md.

[Copilot]

@copilot lift the instructions generation logic out of the scanners (and remove the flag from the scanner context). It looks like AGENTS.md file is pretty much the standard across most environments. I...

Done in 561c11e. Removed agent-specific instruction file creation from all scanners and centralized it in McpInitCommand. Now creates AGENTS.md at the workspace root, or AGENTS.aspire.md if AGENTS.md already exists. The CreateAgentInstructions flag has been removed from the scanner context.

[mitchdenny]

@copilot Change the logic so that instead of prompting for instruction files and playwright it just adds additional applicators.

In the case of the agent file we only want it added once so we need a flag on the context object which notes that the agent instructions were added so that subsequent scanners don't add an applicator for it. This means that the logic to add a playwright mcp ends up being a completely different applicator.

Make sure that even if the aspire MCP is already present that it will still prompt for the playwright one if it is not present.

[Copilot]

@copilot Change the logic so that instead of prompting for instruction files and playwright it just adds additional applicators.

In the case of the agent file we only want it added once so we need ...

Done in ebef8fe. Changed the implementation to add applicators instead of prompts:

1. Removed all prompts - Users now select from a list of applicators
2. Separate applicators - Each scanner adds up to 3 applicators:
   • Configure Aspire MCP server
   • Configure Playwright MCP server
   • Create agent instructions file (added once across all scanners via AgentInstructionsApplicatorAdded flag)
3. Playwright always offered - The Playwright applicator is added even if Aspire MCP is already configured, as long as Playwright itself isn't configured yet
4. Independent checks - Each applicator checks configuration state independently

Users can now select any combination of applicators they want to apply.

[mitchdenny]

@copilot when the AGENTS.md file already exists check if it is the same as the content of the agent instructions we want to drop before proposing the creation of AGENTS.aspire.md. If the content is the same then don't create that applicator.

[mitchdenny]

@copilot remove the logic to generate the AGENTS.aspire.md as a fallback. If there is a AGENTS.md file we just won't offer to create one.

[Copilot]

@copilot remove the logic to generate the AGENTS.aspire.md as a fallback. If there is a AGENTS.md file we just won't offer to create one.

Done in the above commit. Removed AGENTS.aspire.md fallback logic - now the applicator is only offered when AGENTS.md doesn't exist, and it only creates AGENTS.md.