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

With no annotations provided, the description must fully disclose behavioral traits. It mentions that it returns only group counts, which is useful, but it does not disclose side effects (e.g., network access, discarding of parameters), error behavior, or that some schema parameters are explicitly marked as discarded after a shape check. The description's claim to 'fetch' conflicts with the schema's note that some parameters are 'discarded after the shape check,' indicating a lack of transparency about the actual operational scope.

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, which is concise. However, it is under-specified for a tool with nine parameters and no output schema, providing insufficient structure to guide an agent on how to invoke it correctly. It is not overly verbose, but it lacks the necessary detail to be considered well-structured.

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?

Given the tool's complexity (9 parameters, no output schema, no annotations), the description is severely incomplete. It does not explain what 'group counts' refers to, how parameters map to the action, the return format, or error handling. An agent would be left guessing about the actual behavior and usage, making this far below the minimum viable description.

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 has 100% description coverage, so each parameter is self-documented. The tool description adds no additional meaning beyond the schema—it does not clarify which parameter is the robots.txt URL or how parameters relate to the action. Per the rubric, a baseline of 3 is appropriate when the schema does the heavy lifting, and the description does not exceed that.

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 states a specific verb ('Fetch'), a specific resource ('public robots.txt'), and a specific output ('return group counts only'), making the tool's core purpose clear. However, it does not differentiate from siblings like 'fetch-status' or 'domain-shape' beyond the robots.txt target, so it loses a point for not explicitly positioning itself against alternatives.

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 use this tool versus the many siblings (e.g., 'fetch-status', 'web-fetch', 'domain-shape'). It does not mention any preconditions, alternative tools, or scenarios where this should be preferred, leaving the agent to guess based on the name alone.

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