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

With no annotations, the description carries the full burden and does disclose meaningful behavior: the CORS probe actively sends a foreign Origin header and specifically flags wildcard-origin + credentials combinations and arbitrary-origin reflection. That is valuable non-obvious context. It still omits operational details like auth requirements, rate limits, and redirect handling, so it falls short of a 5.

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 a single dense paragraph that front-loads the core action and check list before giving scope and alternatives. Every clause carries information, though the parenthetical enumeration of headers is somewhat long; it is efficient but not maximally tight.

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 single-parameter audit tool with no output schema and no annotations, the description adequately covers what is checked, the active CORS probing behavior, and alternative routing. It gives a hint about return content ('with a score') without needing to detail the full response, leaving only minor operational gaps.

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 coverage is 100% and the single 'url' parameter is already documented in the schema. The description implies what is fetched but adds no format details (scheme requirements, redirects, etc.) beyond what the schema provides, so the 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?

The description names a specific verb and resource ('Fetch a URL and audit its response headers') and enumerates exactly what is checked: specific security headers plus a CORS policy probe. It explicitly distinguishes itself from siblings by routing server/TLS-level checks to ssl_cert_check or ssl_labs_grade, so an agent can select it without opening any schema.

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 states the scope ('Header-level checks on a single response') and names the alternative tools with the condition that selects them ('for server/TLS-level checks use ssl_cert_check or ssl_labs_grade instead'). This is explicit when-to-use and when-to-use-something-else guidance, matching the strongest calibration example.

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