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

With no annotations, the description must carry the behavioral burden. It does state the core behavior plainly and implies a read-only membership check. However, it does not disclose details such as whether subdomains are matched, how empty input is handled, or whether the result is a simple boolean, leaving some behavioral ambiguity.

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 appropriately short for a simple lookup tool and conveys the key purpose in one sentence. The leading 'HSTS Preload:' phrase is somewhat redundant with the title, but it does not meaningfully bloat the description.

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 one-parameter, single-purpose tool this is nearly sufficient: the domain input is implied and an output schema exists. It falls short because parameter format, default behavior, and edge cases like empty queries are not addressed, and no usage or alternative context is provided.

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 0% description coverage, so the description must compensate. It does indicate that the sole parameter 'q' represents a domain, which is the essential semantic. It does not clarify accepted domain format, whether 'www' is included, or what the empty default means, so the compensation is incomplete.

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's function: checking whether a domain is on the browser HSTS preload list. It names a specific resource and an identifiable query action, which distinguishes it from generic domain lookup tools among the siblings. It is not a full 5 because it opens with a near-repeat of the title and relies on the word 'Is' rather than an explicit verb like 'check'.

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 offers no guidance about when to use this tool versus alternatives, nor does it mention exclusions such as domains not in the preload list, subdomain checks, or format expectations. Usage must be inferred entirely from the one-line description.

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