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

The annotations provide good safety coverage (readOnlyHint: true, destructiveHint: false). The description enhances this by detailing the specific behaviors: reporting sizes both with and without compression, which is valuable functional context.

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?

It is a single, concise sentence where every word adds value to the definition, focusing on what the tool does and its specific output.

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 simplicity (one input parameter), the excellent purpose clarity, and the safety annotations, the description is fully sufficient for an agent to select and invoke the tool correctly.

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 schema coverage is 0%, meaning the description must carry the semantic load. Specifying that the 'target' is a URL adds necessary meaning to the string parameter, meeting the minimum viable definition standard.

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 purpose is stated with high specificity: checking whether a URL is served with gzip or Brotli compression. This clearly differentiates it from the various security-focused checks present in the sibling tool list.

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?

While it doesn't explicitly state 'when vs. alternative,' the functional difference between checking compression (performance) and the many other sibling tools (security, structure, metadata) provides clear guidance on its appropriate context.

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