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

With no annotations provided, the description carries the full burden of behavioral disclosure. It accurately says the tool fetches and returns counts, which is a read operation, but it does not disclose network dependency, timeout behavior, SSL requirements, or how robots.txt parsing handles errors or non-standard files. The description also omits what 'group counts' means in edge cases like absent or malformed robots.txt files.

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 one short sentence with no filler. It front-loads the primary action and constrains the output scope immediately. It is appropriately sized for a simple utility, though the mismatch between the stated task and schema parameters is not addressed anywhere in the description.

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 tool with 4 parameters, no required fields, no annotations, and no output schema, this description is thin. It does not explain the purpose of the 'json' and 'zone' parameters, what the group counts look like (structure, format), or how to handle failures and edge cases. An agent has enough to guess the primary use case but not enough to call the tool correctly with confidence.

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 for all four parameters, but the parameters themselves appear mismatched with the tool's stated purpose. The description says 'Fetch a public robots.txt,' yet the schema includes 'json' and 'zone' fields that have no evident connection to robots.txt fetching. The description does not clarify why these parameters exist or how they relate, leaving an agent uncertain about which parameters to populate for the intended task. With 100% schema coverage, baseline is 3, but the mismatch between description and schema parameters lowers the score.

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') and resource ('public robots.txt') and immediately narrows the output to 'group counts only.' This is clear about what the tool does and distinguishes it from any tool that returns the full robots.txt content. However, it does not name a sibling or explain what a 'group' is, so it falls just short of full differentiation.

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 a clear unit of work but provides no guidance on when to choose this tool over alternatives. It does not mention whether the URL must be publicly accessible, whether it follows redirects, what happens on failure, or any constraints like rate limits. There is no explicit when-to-use or when-not-to-use guidance, leaving an agent to infer applicability from the name and description alone.

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