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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, indicating a safe read operation. The description adds little beyond that—'related metrics' is vague, and 'chosen period' is inaccurate given the parameter schema. It does not contradict the annotations, but also does not provide additional meaningful behavioral disclosure.

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 short sentences: one for the core purpose and one pointing to a related tool. It is front-loaded and every word earns its place, with no unnecessary elaboration or repetition.

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?

Given the tool's simplicity (2 optional params, output schema present) and strong annotations, the description is minimally viable. However, it lacks details about what 'related metrics' include, how the ranking is ordered, and the 'chosen period' phrase creates confusion because no period parameter exists. This gap is significant enough to prevent a higher score.

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 input schema has 100% coverage, as both 'type' and 'limit' have descriptions. The description does not add meaning beyond the schema and actually introduces a 'chosen period' concept that does not map to any parameter. Since the schema already explains the parameters, the baseline of 3 is appropriate, but no additional semantic value is provided.

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 clearly states the tool ranks TLDs by registration volume, which is a specific verb and resource. It also mentions 'related metrics' and points to tld_trends as a sibling, providing some differentiation. However, the phrase 'over a chosen period' is misleading because the type parameter only allows 'newly' (today) or 'active' (total) with no actual date range selection.

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 only says 'Related: tld_trends,' which implies an alternative exists but does not explain when to use tld_rank versus tld_trends. No explicit conditions, prerequisites, or exclusions are given. The usage context is thus implied rather than clearly stated.

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