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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, so the mutation profile is known. The description adds that it renames/moves an existing folder and that parent_id is an exact folder ID, but doesn't disclose side effects like whether moving changes child folders or whether renaming affects labels. It doesn't contradict annotations.

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

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

The description is compact and front-loaded with the core action. The repeated ID guidance is somewhat redundant with the schema descriptions, but it's placed efficiently and the critical warning is clear. It earns its place by emphasizing the ID requirement.

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

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

For a mutation tool with no output schema, the description covers the key prerequisites (resolve folder_id, use exact IDs) and the main parameters. It doesn't explain return values or side effects, but the annotations cover the safety profile and the schema covers parameters. The main gap is lack of detail on what happens when moving a folder (e.g., does it affect children), but this is a minor gap for a simple rename/move operation.

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

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

Schema description coverage is 75%, so the schema already documents folder_id, parent_id, and account_id in detail. The description adds the workflow hint 'Resolve folder_id first' and the 'Never pass human folder name' warning, which reinforces the schema. The name parameter is not described in the schema, but its meaning is obvious from the tool name and description. Baseline 3 is appropriate.

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

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

The description states a specific verb and resource: 'Rename/move one existing folder.' It clearly distinguishes from email_create_folder and email_delete_folder. However, it doesn't explicitly contrast with email_move_or_label, which is a sibling that also moves/labels messages, though the folder-specific scope is clear.

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

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

The description gives explicit when-to-use guidance: 'Resolve folder_id first' and 'Obtain with: email_list_folders -> folder.id'. It also provides a clear exclusion: 'Never pass: human folder name such as Inbox when an ID is required.' This tells the agent exactly how to prepare inputs and what not to do.

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