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

Annotations already establish readOnly/openWorld/non-destructive, so the bar is lower. The description adds real prerequisite context beyond the annotations: an API key is required and a free StartupHub.ai account is needed, warning the agent about auth/credential failure modes. It stops short of noting rate limits, credit consumption, or third-party (Ahrefs) data latency.

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?

Three short fragments, front-loaded with the returned metric. Very little waste, though the final two sentences both convey 'you need credentials,' a mild redundancy.

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 single-parameter read tool with no output schema, the essentials are covered: what the value is, its scale, and the credential requirements. The one substantive gap is sibling disambiguation against check_effective_domain_rating.

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?

Only one parameter, and schema coverage is 100% — the schema already documents it in more detail ('Domain or URL, e.g. example.com') than the description's bare 'for a domain'. Baseline 3 applies since the description adds no syntax or normalization rules.

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 verb+resource+return metric: 'Ahrefs Domain Rating, 0 to 100, for a domain.' An agent knows exactly what comes back. It does not, however, distinguish itself from the near-identical sibling check_effective_domain_rating, which is the main ambiguity here.

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 guidance on when to use this rather than check_effective_domain_rating, check_trust_reputation, or scan_company_technology. The only 'guidance' offered is prerequisite-related (API key, account), not situational.

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