asn_lookup

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

Annotations confirm read-only, idempotent, non-destructive. Description adds behavioral details: default truncation at 50 prefixes, promise that counts are honest pre-truncation totals, and rate limits. No contradictions.

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 concise sentences: first states purpose and output, second gives usage, third details parameter behavior. No redundant information; every sentence contributes value.

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?

Covers purpose, usage, parameter behavior, rate limits, truncation behavior, and return format. Output schema existence is noted in context. Complete for a lookup tool with moderate complexity.

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?

Input schema has 100% description coverage. Description adds value beyond schema for include_full_prefixes with a concrete example (Cloudflare AS13335 announces 2500+ prefixes). Target parameter is given example formats.

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 the tool looks up ASN for a domain or IP, returning AS number, organization, and prefixes. It distinguishes from sibling tools like dns_lookup and whois_lookup by being specific to network operator identification.

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?

Describes use case: 'identify network operator and IP range ownership.' Provides guidance on when to set include_full_prefixes=True (network mapping, BGP route audits). Includes rate limits (30/hr free, 500/hr Pro). Lacks explicit 'when not to use' or alternative tool references beyond the implicit context.

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