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

The description aligns with annotations (readOnlyHint=false, destructiveHint=false) by indicating a write operation that is not destructive. It adds the context that it targets Mail.app specifically, but it does not disclose that the 'confirm' parameter must be true or mention any side effects beyond folder creation.

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 a single, focused sentence that front-loads the core action and resource. It contains zero filler or redundant content.

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 simple creation tool with full schema coverage and an output schema, the description provides sufficient context. It could mention the confirm requirement or account behavior, but those are already captured in the schema, and no return-value explanation is needed due to the output schema.

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 100%, so the input schema already describes all three parameters clearly. The description adds no additional parameter-level detail, which is acceptable given the high schema coverage, but it does not compensate for any gaps either.

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 uses a specific verb ('Creates') with a specific resource ('new mailbox folder') and scopes it to 'Mail.app'. This clearly distinguishes it from sibling tools like list_email_folders and move_email.

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?

No guidance is provided on when to use this tool versus alternatives, such as list_email_folders to inspect existing folders or move_email to manage messages. There is no mention of prerequisites, duplicate handling, or when not to use it.

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