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

With no annotations to convey read-only behavior, the description carries the full burden. 'Look up' implies a read operation and 'normalized RDAP data' hints at output transformation, but the description does not disclose error behavior, whether data is fetched live, or how the result is structured beyond listing a few fields.

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 a single focused sentence that front-loads the core action and resource, then lists returned fields without repetition or filler. Every part contributes useful 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?

For a single-parameter lookup tool with full schema coverage and no output schema, the description provides adequate context by specifying the source (RDAP), the normalization, and the key returned fields. It does not explain edge cases such as invalid ASNs or formatting, but the simplicity of the tool makes the definition reasonably complete.

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?

The input schema already fully documents the single 'asn' parameter with an example format and the accepted 'AS' prefix. The description adds no additional parameter-level meaning beyond restating that the lookup is for an autonomous system number, so the baseline of 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?

The description clearly identifies the tool as a lookup operation for autonomous system numbers, names the specific data source (normalized RDAP data), and enumerates the returned fields (holder, country, status, registration dates). This separates it from sibling lookup tools like ip-lookup or domain-lookup by resource type.

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?

The description implies that this tool is for ASN lookups, which is enough to select it over the domain, IP, entity, or nameserver lookup siblings. However, it does not explicitly state when to prefer this tool over alternatives or mention any exclusions or fallback conditions.

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