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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds value beyond them: no API key required, rate-limited, sends no payload (plain GET-style probe), and discloses grading rules and the fact that COOP/CORP/COEP are reported but not graded. It also flags that it surfaces info leaks like server-version disclosure.

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?

Front-loads the core action, then grading detail, then alternatives, in a tight multi-clause structure with no filler. Slightly dense in the header enumeration, but every clause carries routing or behavioral information.

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 read-only audit with annotations and an output schema present, the description covers scoping, safety, auth, rate limits, grading semantics, and sibling alternatives. Nothing an agent needs to invoke it correctly is missing.

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 fully documented in the schema, including the https:// default. The description only adds that redirects are followed from that URL, which is already schema-provided, so baseline 3 is appropriate.

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 (follow redirect chain) and resource (HTTP security headers) with the exact header set and grading scale. It explicitly distinguishes itself from ssl_check and security_scan, so an agent can route correctly 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?

Gives explicit when-to-use ('HTTP-layer/header posture') plus named alternatives with their conditions: ssl_check for certificate/TLS issues, security_scan for a full domain report. When-not guidance is effectively covered by those alternatives.

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