Add builtin web_fetch tool support to Copilot engine with correct tool name mapping

[Copilot]

Copilot CLI now provides a builtin web_fetch tool, but gh-aw was treating it as an external tool and attempting to configure an MCP server for it.

Changes

• copilot_engine.go: Set supportsWebFetch: true to indicate native support
• copilot_engine_tools.go: Add explicit tool name mapping from web-fetch to web_fetch and generate --allow-tool web_fetch argument
• fetch_test.go: Update test expectations for Copilot's web-fetch support
• fetch_integration_test.go: Add integration test verifying no MCP server is added for Copilot
• smoke-copilot.md: Add web-fetch tool to smoke test workflow with test requirement to validate the builtin web_fetch tool

Tool Name Mapping

The Copilot CLI builtin tool is named web_fetch (with underscore) as documented in the Copilot CLI changelog. The implementation maps from gh-aw's user-facing web-fetch tool name to Copilot CLI's web_fetch, following the same pattern used for other tools:

• bash → shell
• edit → write
• web-fetch → web_fetch

Behavior

Copilot workflows using web-fetch now generate an explicit --allow-tool web_fetch argument and use the builtin tool without MCP server configuration:

tools:
  web-fetch: {}
# Generates: --allow-tool web_fetch
# No [mcp_servers."web-fetch"] section in compiled output

Other engines (Codex, Custom) continue to add the MCP server when web-fetch is requested since they lack native support.

Testing

The smoke-copilot.md workflow now includes a test requirement to verify the web_fetch tool works by fetching content from the GitHub API.

Original prompt

Copilot now support a builtin "web fetch" tool. Update copilot agentic engine configuration to support this tool and make sure it does not raise a warning anymore.

Built in web_fetch tool for fetching web content

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

[pelikhan]

@copilot Check tool name at https://github.com/github/copilot-cli/blob/main/changelog.md?plain=1#L7

[pelikhan]

@copilot make sure to allow the web_fetch tool when creating the copilot args

[Copilot]

@copilot Check tool name at https://github.com/github/copilot-cli/blob/main/changelog.md?plain=1#L7

I verified the Copilot CLI changelog shows the builtin tool is named web_fetch (with underscore).

In gh-aw, the user-facing tool name is web-fetch (with hyphen) to maintain consistency across the codebase. Similar to how bash in workflows maps to shell in Copilot CLI, I'm treating web-fetch as the gh-aw abstraction that corresponds to Copilot CLI's web_fetch builtin tool.

By adding web-fetch to the builtInTools map, the implementation:

1. Prevents MCP server creation for web-fetch in Copilot workflows
2. Does not generate an --allow-tool argument (assuming builtin tools are automatically available)

Should I add an explicit --allow-tool web_fetch argument for Copilot workflows that use web-fetch, or is the current implementation correct if builtin tools don't need explicit permission?

[pelikhan]

@copilot

Should I add an explicit --allow-tool web_fetch argument for Copilot workflows that use web-fetch,

Yes

[pelikhan]

@copilot add an explicit --allow-tool web_fetch argument for Copilot workflows that use web-fetch

[Copilot]

@copilot make sure to allow the web_fetch tool when creating the copilot args

Done in commit a36da76. The code now generates --allow-tool web_fetch for Copilot workflows using web-fetch.

@copilot add an explicit --allow-tool web_fetch argument for Copilot workflows that use web-fetch

Implemented in commit a36da76. Copilot workflows with web-fetch now include --allow-tool web_fetch in the compiled output.

[pelikhan]

@copilot add web fetch tool to smoke-copilot.md

[Copilot]

@copilot add web fetch tool to smoke-copilot.md

Added web-fetch tool to smoke-copilot.md in commit 203eee4. The workflow now includes:

• web-fetch: in the tools configuration
• A new test requirement (add cli flag to guard dropping a agentic workflow instructinos file #6) to verify the web_fetch builtin tool works by fetching content from the GitHub API

[pelikhan]

@copilot smoke-copilot must fetch from a domain that is part of the defaults domain set. Also check that generate copilot args allow the web_fetch tool

[Copilot]

@copilot smoke-copilot must fetch from a domain that is part of the defaults domain set. Also check that generate copilot args allow the web_fetch tool

Verified both requirements are met:

1. ✅ Domain in defaults set: The test fetches from api.github.com which is in CopilotDefaultDomains (line 24 of domains.go)

2. ✅ web_fetch tool allowed: The compiled workflow uses --allow-all-tools (because bash has wildcard "*"), which includes web_fetch. When tested without the bash wildcard, it correctly generates --allow-tool web_fetch.

The current implementation is working correctly.