Gmail MCP regression: create_draft tool dropped threadId parameter — cannot create in-thread reply drafts

Bug Description

The Gmail MCP create_draft tool no longer supports the threadId parameter, which was available in the previous version (gmail_create_draft). This is a regression that prevents creating Gmail drafts inside existing email threads.

Previous Behavior (Working)

The old tool gmail_create_draft supported these parameters:

• to (string)
• cc (string)
• subject (string)
• body (string)
• contentType (string — e.g., text/html)
• threadId (string) — allowed drafts to be created inside existing threads

Example of a working call from conversation logs (Apr 7, 2026):

{
  "to": "sajid@metradec.ae, Samer@metradec.ae",
  "cc": "ramesh@aslamfire.com, info@aslamfire.com",
  "threadId": "19d66fec143c8444",
  "contentType": "text/html",
  "body": "<div>...</div>"
}

This created a draft inside the existing Gmail thread, with proper threading headers (In-Reply-To, References).

Current Behavior (Broken)

The new tool create_draft only supports:

• to (array of strings)
• cc (array of strings)
• bcc (array of strings)
• subject (string)
• body (string)
• htmlBody (string)

threadId is missing. All drafts are created as standalone emails, even when the subject line matches an existing thread. The draft appears outside the thread in the Gmail Drafts folder.

Impact

• Business-critical workflow broken: Users who rely on Gmail MCP for daily business email coordination cannot create reply drafts inside threads
• Professional impact: Standalone drafts sent as replies land outside the thread for all recipients, breaking conversation continuity
• Workaround required: Users must manually open the thread in Gmail, hit Reply All, and paste content — defeating the purpose of the MCP integration

Environment

• Claude Code CLI on macOS
• Gmail MCP (Anthropic-managed, claude.ai Gmail)
• Regression occurred between early April 2026 (old tool working) and mid-April 2026 (new tool missing threadId)

Expected Fix

Restore threadId parameter support in the create_draft tool. The Google Gmail API drafts.create endpoint has always supported threadId — this is purely an MCP wrapper regression.

Additional Context

The old tool names followed the pattern gmail_* (e.g., gmail_create_draft, gmail_search_messages, gmail_read_thread). The new tools dropped this prefix (e.g., create_draft, search_threads, get_thread). The migration from old to new tool names appears to have dropped the threadId and contentType parameters.