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

With no annotations, the description carries the full burden. It discloses that it fetches a URL, reports headers with explanations, and additionally flags weak configurations (short HSTS max-age, no includeSubDomains, CSP unsafe-inline/eval). This goes beyond a simple list, though it omits details like redirect handling or timeouts.

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 two sentences, front-loaded with the primary action in the first sentence, and uses the second sentence to add use cases and extra capabilities. Every word contributes without 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?

For a simple one-parameter tool with no output schema, the description covers purpose, use cases, and output behavior thoroughly. It could mention potential limitations (e.g., follows redirects, timeout) but is complete enough for practical use.

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% coverage with a description for the 'url' parameter, so the baseline is 3. The tool description adds no additional parameter-specific meaning beyond the schema, but also does not need to since the schema suffices.

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 action ('Fetch a URL and report which HTTP security headers it sets') with a specific resource (HTTP security headers) and enumerates the exact headers. It also distinguishes from sibling tools by focusing on security header auditing rather than email auth, DNS, or service status.

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?

It provides explicit use cases ('Use to audit a site's header posture or verify a header change is live'), giving clear context for when to invoke the tool. However, it does not mention exclusions or alternative tools, so it falls short of a 5.

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