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

Annotations already establish that this is a safe read-only, non-destructive, non-open-world operation. The description adds useful behavioral detail (result ordering and cursor-based paging) but omits page size, result limits, or what a thread contains.

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?

Three short sentences, front-loaded with the resource and ordering, followed by filtering and paging. No sentence is redundant.

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 6-parameter, zero-required read list with annotations covering safety and no output schema, the description covers ordering, filtering, and paging adequately. Minor gaps remain around default view behavior and page size, both partially covered by the 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?

With schema coverage at 50%, the description compensates by mapping filter dimensions to parameters (unread/view, label/labelId, mailbox/mailboxId, campaign/campaignId) and by explaining that the cursor comes from the previous response. It still does not explain the 'urgent' view or cursor format, so it is not fully complete.

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 the resource (reply threads) and a concrete ordering (newest first), which lets an agent distinguish this from get_thread, the singular sibling. It does not explicitly name the tool as a list operation versus the sibling, keeping it just short of a 5.

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?

It gives clear usage context: filter by unread, label, mailbox or campaign, and resume paging with the cursor from the previous answer. There is no explicit when-not clause or named alternative such as get_thread for a single thread, which is why it is not a 5.

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