fastmcp-gsuite

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modify_gmail_message

Add or remove labels on a specific Gmail message by providing the user account, message ID, and labels to add or remove.

Instructions

Modify labels on a Gmail message (add or remove labels).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "user_id": "<user_id>",
      "message_id": "<message_id>"
    },
    "name": "modify_gmail_message"
  }
}

Input Schema

Name	Required	Description
`user_id`	Yes	The EMAIL of the Google account. Choose from:
`message_id`	Yes	The ID of the Gmail message to modify.
`add_label_ids`	No	Label IDs to add to the message.
`remove_label_ids`	No	Label IDs to remove from the message.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.0Jun 21, 2026

TDQS

B3.2/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden. It only states the basic action without disclosing side effects (e.g., whether labels must exist, sync behavior, error cases). For a mutation tool, this is insufficient.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise with a single sentence that front-loads the purpose. No wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has 4 parameters, no output schema, and no annotations, the description is too minimal. It lacks context about how user_id must be an email, how to obtain label IDs, or any prerequisites. Completeness is low.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

All four parameters have descriptions in the schema (100% coverage). The description adds no extra meaning beyond what the schema already provides for user_id, message_id, add_label_ids, and remove_label_ids.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'modify' and the specific resource 'labels on a Gmail message', with explicit mention of add or remove actions. This distinguishes it from sibling tools like archive (adds a system label) or batch_modify (multiple messages).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidelines are provided about when to use this tool versus alternatives like batch_modify_gmail_messages or archive_gmail_message. There is no mention of prerequisites, such as needing to retrieve label IDs first via get_gmail_labels.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.