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

With no annotations, the description must carry the behavioral burden. It discloses that only group counts are returned (not full content), which is useful. However, it does not mention response format, error handling, or side effects (e.g., no disk access, rate limits), leaving many behaviors unspecified.

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, front-loaded sentence with zero filler. It states the action and the output scope immediately, making it easy to parse. Concise without being under-specified for its purpose.

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?

Despite a 9-parameter schema, the description does not connect any parameter to the actual operation. It omits which input (e.g., url) is needed to fetch a robots.txt and disregards the many 'discarded after' parameters, creating confusion. The output is vaguely described as 'group counts only' without structure. Given the schema's breadth, a richer description is required to guide correct invocation.

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 descriptions cover 100% of parameters, so the baseline is 3. The description adds no parameter-specific information beyond the schema, relying entirely on the schema's per-param details. It does not clarify which parameter (e.g., url vs host) is required for the robots.txt fetch, so it adds no incremental value.

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 a specific action: fetch a public robots.txt and return group counts. The verb 'fetch' and resource 'robots.txt' are unambiguous, and the scope ('group counts only') is explicit. However, it does not differentiate from sibling tools like web-fetch or fetch-status that could also fetch URLs, so it lacks explicit sibling separation.

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?

No guidance is provided on when to use this tool versus alternatives. The description does not mention prerequisites, scenarios, or exclusions, nor does it reference sibling tools like web-fetch or normalize-url. An agent would have to infer usage from the name alone.

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