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

Annotations already declare readOnly, idempotent and non-destructive behavior, and the description adds meaningful context beyond that: the underlying data source, its coverage thresholds, and that a missing domain is reported explicitly rather than silently. It stops short of describing result shape in detail or any freshness/caching behavior.

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?

Two sentences, front-loaded with what the tool returns before moving to coverage limits. Every clause conveys information an agent would otherwise have to guess at; nothing is redundant with the name or annotations.

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 does the work of explaining what comes back (a count and the strongest referrers) and how absence is signalled. Coverage limitations are disclosed in a way that prevents misinterpretation of empty results. Only minor gaps remain, such as whether results are ordered or limited.

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 single parameter has full schema coverage with its own description and an example, so the schema carries the burden. The description does not add format constraints (e.g. whether subdomains or URLs are accepted) beyond what the schema already supplies, so the baseline applies.

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?

States a specific resource and what it returns: the number of referring domains plus the strongest referrers, sourced from the Common Crawl domain web graph. This is clearly distinct from the sibling tools (check_page, check_llms_txt, check_ai_crawler_access), which are page-level checks rather than link-graph queries.

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 defines the data's coverage envelope (.eu, EU/UK country domains with 100+ referring domains, plus the 5,000 most-linked sites), which tells an agent when results will be available versus empty. It does not explicitly name an alternative tool or state a 'use this instead of X' rule, so it stops short of full routing guidance.

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