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

Annotations already mark the operation as read-only, idempotent, and non-destructive, so the description does not need to restate those. It adds useful behavioral detail by defining the terminology ('labels on Gmail') and specifying the returned counts (message and unseen), which goes beyond the raw 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?

The entire description is a single, well-structured sentence that leads with the action, then the resource, then the output detail. Every phrase earns its place, and there is no redundant or filler content.

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 simple read-only listing tool with a single required parameter, the description covers what it does, what it returns (counts), and the scope (one account). No output schema exists, but the description provides enough information about the result shape for an agent to use the tool 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?

Schema description coverage is 100%, and the parameter account is already documented as 'Account id from list_accounts'. The tool description adds only that the tool works on 'one account', which is not meaningfully additional to the schema. Baseline 3 is appropriate because the schema carries the parameter semantics.

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 uses a specific verb ('Lists') with a clear resource ('folders (labels on Gmail)') and explicitly scopes it to a single account. It also tells the agent what data is returned (message and unseen counts), making the tool's purpose unambiguous and distinct from generic sibling tools.

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 implies the tool is for retrieving folders/labels for one specific account, which is the natural context for use. It does not explicitly discuss alternatives or when not to use it, but no sibling tool appears to duplicate this function, so an exclusionary note is less critical.

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