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

Annotations already indicate read-only, idempotent, non-destructive. Description adds valuable context: it does not execute JavaScript or bypass access controls, and it returns only allowlisted headers, implying some filtering. No contradictions with annotations.

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?

Three concise sentences: one for purpose, one for usage constraints, one for fresh parameter. Every sentence adds value with no redundancy.

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 simplicity, output schema existence, and annotation coverage, the description provides all necessary information (purpose, constraints, parameter guidance). No gaps identified.

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 covers both parameters (100%). Description adds meaningful usage guidance for the 'fresh' parameter, explaining cache reuse and cost implications, which goes beyond the schema's technical description.

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 tool returns allowlisted response headers for public URLs. It distinguishes itself from many sibling url tools by specifying it returns only headers and is limited to public resources, but does not explicitly compare with similar tools like web.url.security_headers.

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?

Provides guidance on using for public HTTP(S) resources only, not executing JS or bypassing access controls. Explains when to set fresh=true versus false. However, it does not explicitly tell when to choose this tool over other url header-related siblings.

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