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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful operational behavior: a 2-credit cost, free execution when no results are found, free repeats of known-empty lookups, exclusion of large generic sites, and a ranking/top-100 behavior. This goes beyond the annotations without contradicting them.

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 three focused sentences: what the tool returns, its cost and free conditions, and its return format. It is efficiently structured with no filler, and the most important functional constraints are front-loaded.

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?

The description covers the core purpose, cost, free-behavior edge cases, exclusion criteria, ranking output, and default/max limits. It lacks only a note on pagination or the semantic meaning of 'rank', but nothing an agent needs to decide to call the tool is missing.

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%, so all three parameters are already documented with types and descriptions. The description reinforces the default limit and target scope but does not add material semantics beyond the schema. The confirm_quote_id parameter is not mentioned, but it is not relevant to a 2-credit tool, so the schema's explanation suffices.

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 identifies the tool's output: domains sharing the most referring domains with a target, along with rank and shared-domain counts. It also notes the large-generic-site exclusion illustrative of domain-specific behavior. However, it does not explicitly contrast with the sibling `backlinks_compare` tool, so differentiation is implied rather than stated.

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 explains what the tool returns but provides no explicit guidance on when to choose it over alternatives such as backlinks_compare, backlinks_list, or backlinks_referring_domains. There is no 'use this when...' statement or exclusion of alternative scenarios. Usage is only implied by the tool's name and output description.

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