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

The description explicitly claims idempotency ('Repeating the same operation does not create another folder'), but the annotations declare idempotentHint=false, which directly contradicts this. This is a serious inconsistency that could mislead an agent. Additionally, no other behavioral traits (permissions, error handling, etc.) are disclosed, and with no other annotations to cover the burden, this is a significant failure.

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 two sentences long and front-loads the core action first. The second sentence clarifies a key behavior (no duplicate folders). Every word earns its place, and there is no filler. It is optimally concise for the purpose.

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?

Given that this is a mutation tool with three required parameters and an output schema, the description is under-specified. The contradiction about idempotency creates confusion about expected behavior. It doesn't mention what happens if the folder already exists, what the response contains (though output schema exists), or any required permissions or mailbox validation. The tool's complexity is moderate, but the description leaves critical behavioral questions unanswered, especially the idempotency mismatch.

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 input schema covers all three parameters with descriptions (100% coverage), so the schema already documents each parameter's meaning. The description adds no extra parameter-level detail beyond the schema, so the baseline 3 is appropriate. The description's reference to 'named folder' aligns with the folder parameter but doesn't add new information.

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 action ('Create a named folder') and the scope ('in one mailbox'), which is clear and unambiguous. It also distinguishes the tool from siblings by focusing on folder creation rather than message operations. No ambiguity about what resource is affected.

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 clearly states the action and the target ('in one mailbox'), implying it should be used for creating folders. There are no sibling tools for folder creation, so explicit alternative routing isn't needed. However, it doesn't mention prerequisites like mailbox existence or when not to use it, but given the context, this is a minor gap.

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