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

Annotations already establish read-only, open-world, idempotent, non-destructive behavior, and the description adds substantial context: exact return shape, meaning of asName, countryCode as allocation country rather than server location, BGP-not-geolocation caveat, no city data, CDN nuance, and no login required.

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 dense but front-loaded, first stating the core lookup and return shape, then usage guidance, then important caveats. Every sentence contributes operational meaning without repetition.

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 compensates by describing the return object structure and field semantics. It also covers the main interpretive pitfall: BGP network ownership versus actual web hosting/geolocation.

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?

There is only one parameter, and schema description coverage is 100%, so the schema already documents the domain argument. The description adds no additional parameter syntax or constraints beyond what the schema provides, making 3 the appropriate baseline.

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 IP addresses for a domain and identify the announcing network via ASN, AS name, BGP prefix, registry, and country. It clearly distinguishes itself from detect_web_host by explaining that BGP network ownership is not the same as web hosting.

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?

Explicitly says to call this when asked what IP a domain resolves to or which network owns that IP, and explicitly redirects "who hosts this site?" questions to detect_web_host. This gives both when-to-use and when-not-to-use guidance with a named alternative.

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