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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine behavioral context beyond that: results are ordered 'strongest first' and each row carries authority, link counts, dofollow counts, and first/last seen dates, which tells the agent what it will receive without an output schema.

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, no filler, with the core definition front-loaded and the use case trailing. Slightly dense in the first sentence's field enumeration, but every element earns its place.

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 usefully enumerates the returned fields and their ordering, which is exactly the gap it needs to fill. It stops short of describing pagination limits or behavior at large result sets, but that is a minor omission for a simple two-parameter read tool.

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?

Schema coverage is 100% for both parameters, so the schema already documents 'domain' and the 1-100 limit. The description adds no new syntax or constraint detail beyond the ordering hint; baseline 3 is correct when the schema does the heavy lifting.

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 and resource ('list of websites that link to a domain') and names the canonical term 'referring domains' in parentheses, so the tool's identity is unambiguous. However, it never distinguishes itself from the highly confusable sibling backlinks_summary, leaving the agent to infer the boundary.

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?

'Use for link-building research and competitor backlink analysis' gives an implied scenario, but there is no when-not guidance and no alternative named despite backlinks_summary and domain_overview being obvious candidates for the same intent. Usage is suggested rather than routed.

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