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

Annotations already mark it as readOnly and non-destructive. The description adds 'No key needed', which is a useful behavioral note about authentication, and the example indicates the tool returns operator name and ASN. However, it doesn't disclose whether results are paginated, sorted, or limited—though the schema covers the limit parameter. The description adds value beyond annotations without contradicting them.

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 two sentences, front-loaded with the core purpose, then the key note and an example. It is efficient and has no filler. The example could be considered optional but is concise enough to be justified.

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?

Without an output schema, the description should clarify what the tool returns. The example shows 'Cloudflare, Inc. as AS13335', which implies the result includes operator name and ASN, but does not explain the response structure (e.g., list format, fields, sort order). It also doesn't mention default or pagination behavior beyond the limit parameter description in the schema. Given the tool's complexity (no nested objects, few params), the gap is moderate.

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%, with each parameter already described (q, limit, country). The tool description adds an example that maps q and country to a real query but does not explain limit beyond the schema. The example reinforces parameter usage but adds marginal semantic value given the schema's clarity.

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 states the action 'Search the ASN directory for a network operator' with a specific resource (ASN directory) and provides an illustrative example. While it does not explicitly distinguish from the sibling 'asn_lookup', the resource and action are clear enough for an agent to infer its purpose.

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 provides no guidance on when to choose this tool over siblings like 'asn_lookup'. It only mentions 'No key needed', which is a convenience, but does not explain the difference between searching by name/domain and looking up a specific ASN. There is no 'use this when' clause. The example is illustrative but not a usage guideline.

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