asn_lookup

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

Adds significant value beyond annotations: discloses truncation behavior (first 50 prefixes), honest pre-truncation counts, and exact return fields. Annotations already indicate read-only, idempotent, non-destructive.

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?

Concise, front-loaded with purpose, then usage guidelines, rate limits, and return format. No extraneous text.

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?

Given the simple tool with 2 parameters and no nested objects, the description covers all necessary information: purpose, usage, rate limits, output fields, and behavioral nuances.

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 covers 100% of parameters with descriptions. Description adds contextual guidance on default behavior and when to use include_full_prefixes, providing an example (Cloudflare).

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?

Description clearly states it looks up ASN for a domain or IP, returning AS number, organization, and prefixes. Distinct from sibling tools like dns_lookup or ip_lookup.

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 clear usage context: identifying network operator and IP range ownership. Includes guidance on when to set include_full_prefixes with specific use cases like network mapping. Rate limits are mentioned.

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