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

Annotations already declare readOnlyHint and openWorldHint, so safety and external-query behavior are covered. The description adds genuinely new behavioral content by naming what is retrieved — reverse DNS, RPKI validity, geolocation — which is the closest thing to a return-value contract given there is no output schema. It omits edge-case behavior (invalid input, private/reserved ranges, rate limits).

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, zero filler, front-loaded with the operation and its outputs before the usage guidance. Every clause 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 data fields and gives usage context, which is enough to call the tool correctly. Missing only peripheral details such as failure behavior for malformed or private inputs.

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 description coverage is 100% and the single 'input' parameter is documented in the schema as 'IPv4/IPv6 address or ASN like AS13335'. The description only restates 'IP address or ASN' with no additional format, normalization, or error guidance, so the baseline of 3 applies.

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 ('look up an IP address or ASN') and enumerates the five data classes returned (owner org, prefix, PTR, RPKI, geolocation). The IP/ASN input scope naturally separates it from the check_* siblings, but no sibling is named, so it stops short of explicit differentiation.

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 two concrete use cases: identifying who is behind an address seen in logs, and checking PTR/RPKI for a mail or BGP issue. That is clear when-to-use guidance, though there are no when-not conditions and no explicit routing to check_dns or the other siblings.

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