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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered; the description then adds real value beyond them: unseen targets yield listing_status 'not_seen', lookalike-domain hints may be included, publisher domains can return multiple matches, and no live network request is issued. That is a meaningful behavioral profile; auth/permission or rate-limit details are the only notable omissions.

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?

Purpose is front-loaded in the first sentence and the remaining sentences each add distinct behavioral information without filler. Formatting is somewhat fragmented into short standalone lines, but nothing is wasted.

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?

With no output schema, the description correctly compensates by describing return semantics ('not_seen', lookalike hints, multiple matches for publisher domains) and the no-live-request behavior. Given one parameter and read-only annotations, this is largely complete; only auth/permission expectations are unspecified.

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 0% schema coverage on a single card_url parameter, the description must carry the load, and it does: it discloses that the tool accepts a card URL, endpoint URL, or publisher domain, expanding what the lone schema field actually represents. This is a genuinely useful clarification, though it creates mild ambiguity about whether the value must specifically be a card_url as the schema name implies.

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 gives a specific verb (read stored checks) and resource (card URL, endpoint URL, publisher domain), and clarifies the tool works against cached/stored data rather than a live check. It does not, however, name or contrast itself with the sibling get_agent, so the agent has to infer the boundary itself.

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?

There is no explicit when-to-use or when-not-to-use statement, and no alternative is named. The agent must infer from 'stored checks' and 'no live request' that this is the cached-lookup variant, but no selection guidance is given against get_agent or search_agents.

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