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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds value beyond that by disclosing the output shape (grade, missing items, version exposure) and the per-call price, though it says nothing about auth requirements or rate limiting.

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?

A single front-loaded sentence that packs the action, the specific headers checked, the grading scale, the output contents, and cost. No filler and nothing an agent must read past to find the core purpose.

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 one-parameter read-only tool, the description covers purpose and return content well, and no output schema exists so the summary of results is what the agent has. Minor gap: no mention of whether it follows redirects, requires an API key, or how errors on unreachable domains behave.

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?

There is one parameter with 100% schema description coverage, including an example format, so the schema fully documents input. The description adds no extra detail about URL normalization (scheme optional? path ignored?) beyond what the schema already says, so baseline 3 applies.

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?

States a specific verb and resource ('Grade a website's HTTP security headers') and enumerates the concrete outputs: A-F grade, missing-header list, and exposed server version. This clearly separates it from siblings like email_security, ssl_certificates, and tech_stack, which cover adjacent but distinct concerns.

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 narrow, obvious purpose implies when to call it, and the inclusion of 'Price: $0.001 per call' hints at a cost consideration. However, it never names an alternative tool or states when NOT to use this (e.g., for email-specific headers, use email_security instead), leaving routing to inference.

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