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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful non-schema context — the 'Cost: 1 credit' billing disclosure — but omits failure behavior (private/reserved IPs, invalid input) and any rate or quota context.

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 short fragments with zero filler and the credit cost front-loaded alongside the payload summary. It is efficiently sized, though the telegraphic style makes it read as field names rather than a coherent statement.

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?

An output schema exists, so return values needn't be spelled out (the description nonetheless lists them, partially duplicating it). The critical gap is input-side: nothing tells the agent what an acceptable 'ip' value looks like. For a one-parameter tool this is the only thing the description needed to add, and it did not.

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 required 'ip' parameter has 0% schema description coverage and the description says nothing about it — no IPv4 vs IPv6 acceptance, no format example, no domain-name rejection rule. The only schema signal is type:string, which the description does not build on.

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 is a fragment listing returned attributes (owner, ASN, country, hosting type, rDNS) rather than a stated action; combined with the name and title an agent can infer it enriches an IP, but the description itself never says what it does. It also gives no explicit differentiation from the many lookup_* siblings, which are separated only by their resource in the tool name.

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 when-to-use guidance, no mention of when a different lookup_* tool applies, and no prerequisites. An agent must infer usage entirely from the tool name.

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