Insiders docs for OSS

[mattdholloway]

Summary

Docs update for insiders mode

Why

Fixes https://github.com/github/copilot-mcp-core/issues/1148

What changed

MCP impact

• No tool or API changes
• Tool schema or behavior changed
• New tool added

Prompts tested (tool changes only)

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)

[Copilot]

Pull request overview

This PR adds documentation for the Insiders Mode feature, which provides early access to new features and experimental tools for both local and remote GitHub MCP servers.

Changes:

• Documents insiders mode configuration for the remote server (via URL path /insiders or X-MCP-Insiders header)
• Documents insiders mode configuration for the local server (via --insider-mode flag or GITHUB_INSIDER_MODE environment variable)
• Adds new URL path patterns for combining insiders mode with other modifiers

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
README.md	Adds insiders mode documentation in both remote and local server sections with configuration examples
docs/remote-server.md	Adds comprehensive insiders mode documentation including headers, URL patterns, and combination examples

[Copilot]

The URL path patterns list includes /insiders/readonly (line 124) for combining both modifiers on the default toolset, but similar combinations are not shown for /x/all/ or /x/{toolset}/ patterns. For consistency and completeness, consider adding /x/all/insiders/readonly (or /x/all/readonly/insiders) and /x/{toolset}/insiders/readonly (or /x/{toolset}/readonly/insiders) to the list, or clarify in the note whether these combinations are supported via path or only via headers.

See below for a potential fix:

- `/x/all/insiders/readonly` - All available toolsets with insiders mode in read-only mode
- `/x/{toolset}` - Single specific toolset
- `/x/{toolset}/readonly` - Single specific toolset in read-only mode
- `/x/{toolset}/insiders` - Single specific toolset with insiders mode enabled
- `/x/{toolset}/insiders/readonly` - Single specific toolset with insiders mode in read-only mode

Note: `{toolset}` can only be a single toolset, not a comma-separated list. To combine multiple toolsets, use the `X-MCP-Toolsets` header instead. Path modifiers like `/readonly` and `/insiders` can be combined via path segments (for example, `/insiders/readonly`, `/x/all/insiders/readonly`, `/x/{toolset}/insiders/readonly`) or with the `X-MCP-Insiders` and `X-MCP-Readonly` headers.