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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the description's 'Read-only' is redundant but harmless. It adds meaningful extra behavioral context: 'requires no API key; rate-limited.' This helps the agent anticipate authentication needs and possible throttling.

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 well-structured and front-loaded, opening with the operation and expected output before usage guidance and constraints. One minor inefficiency is that the final sentence repeats the return values already listed in the first sentence, but this is a small redundancy.

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?

The tool has only one input parameter, a high-coverage schema, an output schema, and annotations covering safety and idempotency. The description adds the remaining necessary context: use cases, an explicit alternative, authentication requirements, and rate limits. Nothing essential is missing.

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% and the query parameter already includes examples and allowed forms ('1.1.1.1' or 'AS13335'). The description adds no new parameter-level details, so the schema carries the semantic burden. Baseline 3 is appropriate.

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 opens with a specific verb ('Look up') and names the resource (Autonomous System / BGP information for an IP or AS number), plus the concrete data returned: operator, prefixes, abuse contact, and classification. It also names reverse_dns as a distinct sibling, making the tool's purpose easy to differentiate.

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 gives explicit when-to-use context ('identify who runs a network or whether an IP is cloud/CDN-hosted') and names the alternative tool with the condition for using it ('Use reverse_dns instead for the host-level PTR name of a single IP'). This is clear routing guidance for an agent.

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