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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive) and the description still adds rich operational context beyond them: 1 kB body fetch cap, final-response-after-redirects grading, max 4 redirects each re-checked, ports 80/443 only, 422 on refused targets (not charged), per-target-host rate limit, and 0.3-2 s timing. This is exactly the extra context annotations cannot carry.

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?

Purpose is front-loaded and most clauses are load-bearing (returns, redirects, refusals, limits). The pricing and free-tier-pool enumeration is somewhat long relative to the single-parameter operation, but it is decision-relevant for cost-aware agents, so the length is mostly justified.

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?

There is no output schema, yet the description fully explains the return shape: `score` 0-100, `grade` A-F, every `deduction` with reason, redirect chain, and `upgraded_to_https`. Combined with fetch constraints, rate limits, and pricing, an agent has everything needed to call and interpret the tool.

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?

Only one parameter with 100% schema description coverage, so the schema already documents `url` (public http(s), length bounds). The description restates 'http/https' and 'public' but adds no syntax or format detail beyond the schema, matching the baseline-3 expectation when the schema does the heavy lifting.

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 up front: 'grade a public page's HTTP security headers.' It then enumerates exactly what is graded (HSTS, CSP, cookie flags, COOP/COEP/CORP, disclosure headers), leaving no ambiguity about scope. An agent can distinguish this from render_page, get_page_meta, or inspect_domain at a glance.

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?

Explicitly bounds usage: 'It grades one response's headers, not the site... and it is not an audit,' and notes private/internal/IP-literal targets are refused. This gives clear when-not conditions, though it never names a specific sibling to prefer for related needs (e.g., get_page_meta for metadata), so it stops short of full alternative routing.

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