list_folders

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

Annotations only cover read-only/no-open-world safety, so the description earns credit for disclosing a non-obvious output behavior: content is framed by two marker lines bearing a per-call 16-character hex tag, and only the end marker with this call's tag terminates content. This injection-resistance detail cannot be inferred from the schema or 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?

Two sentences, with purpose front-loaded in the first. The second sentence is dense but justified, though 'Marker-like text without it is part of the message' partially restates the preceding sentence and could be tightened.

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?

With no output schema, the description must carry return-value framing, and it does explain folder names, counts, and marker delimiters. It stops short of clarifying whether counts are total or unread, and says nothing about folder nesting or ordering.

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 takes zero parameters, so there is nothing to document and the baseline of 4 applies. The description correctly adds no spurious parameter discussion.

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?

Opens with a specific verb+resource ('List the mailbox folders') and adds the returned data ('their message counts'), which distinguishes it immediately from the message-oriented siblings (search_emails, get_email, get_thread). An agent can select it without reading any schema.

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?

Usage is only implied: the tool is evidently for enumerating the folder structure before drilling into messages, but the description never says when to prefer it over search_emails or that it takes no filters. No exclusions or alternatives are named.

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