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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful non-schema context: the data source (internet registries/RDAP) and the per-call cost ($0.002 USDC via x402), which matters for a paid tool. It still doesn't mention rate limits or failure behavior for unregistered ranges.

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 purpose and return payload, then invocation and cost in a compact second sentence. The returned-field list is long but each item is informational for a tool with no output schema, so it earns its space.

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?

There is no output schema, so the description's enumeration of returned fields is doing necessary work, and the cost/source disclosure covers the x402 payment aspect. Combined with annotations covering the safety profile, an agent has everything needed to call this correctly.

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%, so both parameters are already documented. The description restates the ip/asn alternatives and implies mutual exclusivity but adds no format details (e.g. ASN prefix handling) beyond the schema, 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 (lookup) and resource (IP address / ASN) plus the data source (RDAP) and enumerates the returned fields (network name/range, org, country, origin ASN, abuse contact, registration dates, reverse DNS). It does not distinguish itself from close siblings like ip_asn or ip_cidr, so an agent cannot fully rule those out from this description alone.

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?

It tells the agent how to invoke it ('Pass ip= (IPv4/IPv6) or asn='), implying the two inputs are alternatives, but gives no when-to-use/when-not guidance and never mentions the competing siblings ip_asn, ip_cidr, or ip_risk. Usage is implied rather than framed.

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