MCP Tools Reference: gmailmcp.googleapis.com

Tool: label_thread

Adds labels to an entire thread in the authenticated user's Gmail account. This operation affects all messages currently in the thread and any future messages added to it.

If unsure of the thread ID, use the search_threads tool first.

If unsure of a user label's ID, use the list_labels tool first to discover available labels and their IDs. To add a trash label or a spam label on to a thread, please use the apply_sensitive_thread_label tool instead.

The following sample demonstrate how to use curl to invoke the label_thread MCP tool.

Curl Request 
curl --location 'https://gmailmcp.googleapis.com/mcp/v1' \
--header 'Authorization: Bearer YOUR_ACCESS_TOKEN' \
--header 'content-type: application/json' \
--header 'accept: application/json, text/event-stream' \
--data '{
  "method": "tools/call",
  "params": {
    "name": "label_thread",
    "arguments": {
      // provide these details according to the tool's MCP specification
    }
  },
  "jsonrpc": "2.0",
  "id": 1
}'

Input Schema

Request message for LabelThread RPC.

LabelThreadRequest

JSON representation 
{
  "threadId": string,
  "labelIds": [
    string
  ]
}
Fields
threadId

string

Required. The unique identifier of the thread to add labels to.
labelIds[]

string

Required. The unique identifiers of the labels to add. Can be a system label ID (e.g., 'INBOX', 'STARRED', 'UNREAD', 'IMPORTANT') or a user-defined label ID. The tool accepts label_ids and not label names. Use the list_labels tool to get the corresponding label id to a display name for user-defined labels.

Output Schema

Response message for LabelThread RPC.

Tool Annotations

Destructive Hint: ❌ | Idempotent Hint: ✅ | Read Only Hint: ❌ | Open World Hint: ❌

Authorization Scopes

Requires one of the following OAuth scopes:

  • https://mail.google.com/
  • https://www.googleapis.com/auth/gmail.modify