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

With no annotations, the description carries the full burden. 'List emails' clearly implies a read-only operation, and the filter options add behavioral detail. It does not explicitly state side effects, but for a list operation this is sufficient; the description adds context beyond the schema by defining the action.

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, front-loaded with the core action and followed by optional filters. Every word earns its place, with no redundancy or 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 simple two-parameter, read-only tool with no output schema, the description is complete. It states the resource, the action, and the filter parameters. It does not mention response format or pagination, but these are not required for a basic list operation and the description sufficiently guides invocation.

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%, as both q and from have descriptive text in the schema. The description merely restates these parameters ('keyword (q)' and 'sender (from)') without adding new meaning. Thus the baseline of 3 is appropriate.

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 ('List') and identifies the exact resource ('emails in your inbox'), clearly distinguishing it from siblings like read_sent, get_email, and send_email. The mention of 'inbox' and optional filters provides clear operational scope.

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 states the tool lists inbox emails and gives filtering options, which provides clear context for when to use it. It does not explicitly name alternatives or exclusions, but the 'inbox' specification and sibling names make the intended use obvious.

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