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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe read-only nature is covered. The description adds that it filters to only folders with unread messages, which is useful behavioral context, but it does not describe the return shape or any pagination details.

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?

Two short sentences with no wasted words. The core behavior is front-loaded, and the secondary usage hint follows immediately without bloating the definition.

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 zero-parameter, read-only summary tool with annotations covering the safety profile, the description is mostly complete. It could clarify whether the result is a list of folder names, unread counts, or both, but an agent can still select and invoke it correctly.

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?

The tool has zero parameters, so there are no parameter semantics to document. The schema coverage is 100% and the description needs no additional parameter detail, making the baseline of 4 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: returns only folders that contain unread messages. It is clear what the tool does, but it does not explicitly distinguish itself from siblings like list_mailboxes or mailbox_status that also return mailbox-related data.

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 phrase 'Es el punto de partida para organizar' implies this is used as an initial organizing step, which gives some usage context. However, it does not state when not to use it or name alternative sibling tools for other mailbox views.

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