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

No annotations exist, so the description carries the full burden, and it discloses the two things an agent most needs to know beyond the payload: cost ($0.005 per call) and the payment mechanism (x402/USDC). It also characterizes the return payload in detail, including that prefix lists are sampled. It stops short of stating failure behavior for unknown or unannounced ASNs, so it is not fully complete.

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?

Front-loaded with the trigger condition and tightly packed, with no filler sentences. It runs slightly long by repeating the endpoint paths in the exclusion clause, but every clause carries routing or payload information.

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 and no annotations, the description compensates by enumerating return fields and stating price and payment rail, which is what an agent needs before spending money. The remaining gap is error/empty-result behavior for invalid or dormant ASNs.

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 a single parameter and schema coverage is 100%; the schema already documents that the AS prefix is optional ("15169 or AS15169"). The description adds nothing about the asn argument, so the baseline 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+resource (ASN lookup) and enumerates exactly what comes back: RDAP registry record, AS name, country, RIR, and currently announced IPv4/IPv6 prefixes. It distinguishes itself from the address-lookup and domain-lookup siblings by name, so an agent can pick it without opening a schema.

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?

Explicit when-to-use ("when an agent has an origin ASN and must decide who is behind a network and whether it is still live") plus explicit exclusions routed to alternatives ("Do not use for one address (/v1/red/ip) or for a domain (/v1/red/whois)"). It even positions the call in a sequence: "The natural second call after /v1/red/ip."

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