gmail_read_message does not return CC/BCC headers

[rsclafani]

Description

The gmail_read_message tool only returns four headers: From, To, Subject, and Date. The Cc and Bcc fields are omitted from the response, even when present on the original message.

Impact

Without CC/BCC headers, it's impossible to:

• Know who else is on a conversation
• Construct a proper Reply All
• Avoid accidentally excluding participants from a thread

This affects any workflow where multiple recipients are involved — which is most professional email.

Steps to reproduce

1. Receive an email where the sender has CC'd one or more recipients
2. Use gmail_read_message to read the message
3. Observe that the returned headers object contains only From, To, Subject, and Date
4. The CC'd addresses are not available anywhere in the response

Expected behavior

The headers object should include Cc (and ideally Bcc where available) so that reply drafts can be composed with the correct recipient list.

Additional context

The Gmail API itself returns these headers — they appear to be filtered out by the connector before the response is returned. Related: anthropics/claude-code#28575 (another Gmail connector gap around draft attachments and sending).