Feature Request: Gmail Filter Management Tools (listFilters, createFilter, deleteFilter)

Summary

Request to add Gmail filter management capabilities to the Google Workspace MCP server.

Requested Tools

Use Cases

• Automate inbox organization setup
• Programmatically manage email routing rules
• Set up filters for specific projects or workflows
• Bulk filter management

Technical Reference

Gmail API supports filter management via users.settings.filters resource:
https://developers.google.com/gmail/api/reference/rest/v1/users.settings.filters

OAuth Scope

Requires: https://www.googleapis.com/auth/gmail.settings.basic

Why This Belongs Upstream

Building a separate MCP server for Gmail filters would require either:

1. Duplicating OAuth authentication (users log in twice)
2. Sharing tokens between MCP servers (fragile, non-standard)
3. Building an OAuth proxy (adds complexity)

Since the google-workspace MCP already has Gmail auth, token caching, and refresh logic, adding filter tools there is ~50-100 lines vs ~300-400 lines + auth complexity for a separate server.

Start by locating the Gmail integration and its existing OAuth scope, token caching, and refresh handling. Compare the requested tools with the Gmail users.settings.filters API reference; done means the four listed filter operations are exposed with the required scope and support the stated criteria, actions, and filter IDs.