Configure GitHub MCP defaults: read-only=true, toolset=default, wildcard tools

[Copilot]

Overview

Updates the GitHub MCP server configuration to use more secure and appropriate defaults:

• read-only: true by default (prevents accidental write operations)
• toolset: [default] by default (provides recommended tools for common use cases)
• Uses ["*"] wildcard for tools instead of maintaining long explicit lists
• Copilot CLI automatically includes --allow-tool github when no tools are specified
• Dev workflow dynamically discovers and tests all GitHub MCP tools

Motivation

Previously, the GitHub MCP server defaulted to:

• read-only: false - allowing write operations by default (security concern)
• toolset: all - enabling all toolsets when none were specified (often unnecessary)
• Automatically adding ~50 default tools to the allowed list, creating verbose configurations
• Copilot CLI would not add --allow-tool github when no allowed field was present, preventing access to GitHub MCP server

These defaults could lead to workflows accidentally modifying repository data or including unnecessary API permissions. The new defaults provide a more secure baseline while still allowing users to explicitly opt into write operations and additional toolsets when needed.

Changes

Core Logic

• Modified getGitHubReadOnly() to return true by default (was false)
• Modified getGitHubToolsets() to return "default" by default (was empty string → "all")
• Simplified rendering logic in all three engines (Copilot, Claude, Codex) to remove conditional checks
• Removed automatic addition of default GitHub tools list - now uses ["*"] wildcard instead
• Added --allow-tool github to Copilot CLI when no allowed field is specified
• Updated dev.md workflow to dynamically discover and test all available GitHub MCP tools with Copilot engine

Tools Configuration Simplification

Before (no configuration specified):

tools:
  github:

Generated:

"tools": [
  "download_workflow_run_artifact",
  "get_job_logs",
  ... 45+ more tools
]

Copilot CLI: No --allow-tool github argument (broken)

After (no configuration specified):

tools:
  github:

Generated:

"tools": ["*"]

Copilot CLI: --allow-tool github (allows access to GitHub MCP server)

This change reduces compiled workflow file size by ~7KB each and simplifies the configuration.

Copilot CLI Tool Arguments

When no allowed field is specified, Copilot CLI now automatically includes --allow-tool github to grant access to the GitHub MCP server:

• No allowed field: --allow-tool github (allow all GitHub tools via MCP)
• allowed: ["*"]: --allow-tool github (explicit wildcard)
• allowed: [tool1, tool2]: --allow-tool github(tool1) --allow-tool github(tool2) (specific tools)
• allowed: []: No arguments (no GitHub tools allowed)

Dev Workflow Testing

Updated .github/workflows/dev.md to validate the GitHub MCP configuration:

• Switched from Claude to Copilot engine
• Dynamically discovers and tests all available GitHub MCP tools rather than testing a fixed list
• Instructs the LLM to explore and identify all tools available from the GitHub MCP server
• Tests tools with sensible arguments across multiple categories:
  • Context tools (e.g., get_me)
  • Repository tools (e.g., get_file_contents, list_branches, list_commits, search_repositories)
  • Issues tools (e.g., list_issues, search_issues)
  • Pull Request tools (e.g., list_pull_requests, search_pull_requests)
  • Actions tools (e.g., list_workflows, list_workflow_runs)
  • Release tools (e.g., list_releases)
  • And any other tools discovered from the GitHub MCP server
• Verifies tools are callable and properly configured
• Detects and fails on permission issues
• Provides comprehensive summary of tool invocation results

This approach makes the test workflow more flexible and future-proof, automatically adapting to changes in the GitHub MCP server's available tools.

Examples

Before (no configuration specified):

tools:
  github:

Generated: GITHUB_TOOLSETS=all (no read-only protection), plus 50+ tool names, no Copilot CLI arguments

After (no configuration specified):

tools:
  github:

Generated: GITHUB_READ_ONLY=1, GITHUB_TOOLSETS=default, "tools": ["*"], --allow-tool github

Explicit override (still works):

tools:
  github:
    read-only: false
    toolset: [all]
    allowed: [get_issue, list_issues]  # Explicit tool list still respected

Backward Compatibility

This is a breaking change for workflows that relied on the implicit read-only: false or toolset: all defaults. Users who need write access or all toolsets must now explicitly specify:

tools:
  github:
    read-only: false  # Enable write operations
    toolset: [all]    # Enable all toolsets

Explicit allowed tool lists are still preserved when specified. Only the automatic addition of default tools has been removed.

This trade-off prioritizes security, simplicity, and better defaults over implicit backward compatibility.

Testing

• All unit tests updated and passing (100+ tests)
• Integration tests verified for all three engines (Copilot, Claude, Codex)
• Manual testing confirmed correct behavior for:
  • Default configuration (read-only + default toolset + wildcard tools + Copilot CLI tool arguments)
  • Explicit read-only: false override
  • Custom toolset configurations
  • Explicit allowed tool lists (still preserved)
  • Both local (Docker) and remote (hosted) modes
  • File size reduction: ~7KB per workflow (89.5 KB → 82.5 KB)
  • Copilot CLI --allow-tool github is correctly added when no allowed field is present
• Dev workflow dynamically validates GitHub MCP tool accessibility by exploring all available tools

Migration Guide

Workflows that need write access should add:

tools:
  github:
    read-only: false

Workflows that need all toolsets should add:

tools:
  github:
    toolset: [all]

Workflows that previously relied on the automatic default tools list and need to restrict tools should add:

tools:
  github:
    allowed: [specific, tools, list]  # Explicitly specify allowed tools

Original prompt

The github mcp should be configured to use the default toolset + readonly and allow all tools instead of maintaining a list of tools.

• read only true by default
• default toolset is "default"

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[pelikhan]

@copilot remove the default list of tools for github (remote/local) as they are not needed

[Copilot]

@copilot remove the default list of tools for github (remote/local) as they are not needed

Done in commit 28dd843. Removed the automatic addition of default GitHub tools list. The MCP config now uses "tools": ["*"] wildcard instead of listing 50+ tools explicitly.

This reduces compiled workflow file size by ~7KB each and simplifies the configuration. Explicit allowed lists are still preserved when users specify them.

[pelikhan]

@copilot when no tools are specified, copilot must have --allow-tool github

[pelikhan]

@copilot update dev.md to use copilot, go through each tool of the github mcp and try to invoke it with sensible arguments, check that the tools are configured property (they might fail because of args but at least they got called). Fail on permission issues.

[Copilot]

@copilot when no tools are specified, copilot must have --allow-tool github

Fixed in commit. When no allowed field is specified, Copilot CLI now includes --allow-tool github to grant access to the GitHub MCP server.

The logic handles three cases:

• No allowed field → --allow-tool github
• allowed: ["*"] → --allow-tool github
• Explicit list → --allow-tool github(tool1) etc.

[Copilot]

@copilot update dev.md to use copilot, go through each tool of the github mcp and try to invoke it with sensible arguments, check that the tools are configured property (they might fail because of arg...

Updated dev.md in commit. The workflow now:

• Uses Copilot engine (changed from Claude)
• Tests 13+ GitHub MCP tools with sensible arguments across categories: context, repos, issues, PRs, actions, and releases
• Validates tools are callable and properly configured
• Fails if permission issues are detected (e.g., tool not allowed)
• Provides summary of tool invocation results

The compiled workflow includes --allow-tool github and "tools": ["*"] configuration as expected.

[pelikhan]

@copilot tell the LLM to explore all available tools that belong to github

[Copilot]

Updated in commit. The workflow now instructs the LLM to dynamically discover and test all available tools from the GitHub MCP server, rather than testing a fixed list. This makes the test more comprehensive and adaptable to changes in available tools.

[github-actions]

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