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

Discloses meaningful behavior beyond annotations: it costs 3 lookup credits unless cached, requires user confirmation, and includes a spamScore interpretation caveat. Annotations already cover openWorld and non-destructive behavior, and the output schema handles return structure, so remaining gaps are minor.

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 sentences, front-loaded with what data is returned, followed immediately by cost and confirmation requirements. Every sentence carries actionable information, including the spamScore caveat.

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 one-parameter external lookup with an output schema and annotations covering openWorld and non-destructive behavior, the description covers the critical credit-confirmation constraint. The main remaining gap is that the domain input format is 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?

The sole parameter, domain, has no schema description, and the tool description never specifies format, examples, or whether it accepts root domains versus full URLs. The parameter name is self-explanatory, but at 0% schema coverage the description does not compensate.

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?

Names the resource (backlinks) and enumerates the returned metrics: referring domains, backlink totals, and domain rank. The function is clear, but it does not explicitly contrast with the sibling lookup_domain tool.

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?

Provides a concrete prerequisite: tell the user the 3-credit cost and wait for confirmation before spending. It also warns not to treat spamScore as disavowal guidance. However, it does not state when to use this tool versus lookup_domain or when not to call it.

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