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

Annotations already establish the safe read-only, closed-world profile, so the bar is lower. The description still adds real behavioral substance by defining the matching rule and the deliberate exclusion, telling the agent exactly what will and will not appear in results — though it says nothing about result shape or size.

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, both earning their place: the first gives the rule and the motivation, the second the exclusion and its rationale. Front-loaded with no filler.

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 single-parameter, read-only detection tool with no output schema, the description covers what the agent needs to decide to call it and to interpret the result set. It could go slightly further by pointing at merge_mail_folders as the follow-up action.

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?

There is a single parameter and the schema fully documents it, including the email pattern and a pointer to list_authorized_mailboxes. The description adds nothing beyond the schema, so the baseline 3 applies.

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 (find duplicate mail folders) and precisely defines what counts as a duplicate: same name within the same parent. That definition is the strongest disambiguation possible, though it never names sibling alternatives like list_mail_folders or find_duplicate_gmail_labels.

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 context is clearly implied — 'likely duplicates worth merging' signals this is the discovery step preceding merge_mail_folders — and the description explicitly states a negative case (same name under different parents is not reported). It stops short of naming the merge tool or listing prerequisites.

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