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

Annotations declare readOnlyHint and openWorldHint, so safety is already covered. The description adds genuinely useful behavioral context beyond them: it follows up to 5 redirects and returns a graded n/6 result across named headers, which tells the agent the shape and scope of the operation.

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 dense sentence with the operation front-loaded and no filler; every clause (redirect limit, header list, grading) earns its place.

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?

With no output schema, the description carries the burden of describing returns and does so concisely by naming the six headers and the n/6 grade. It omits error/failure behavior and the exact response structure, a minor gap for a simple read-only 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 exists and schema description coverage is 100%, so the schema already documents the url field including its security constraints. The description adds no format or validation detail beyond 'a URL', so the baseline of 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 (Fetch) plus resource (URL security headers) and enumerates exactly which headers are reported with an n/6 grade. This clearly distinguishes it from siblings like check_ssl or trace_redirects, which cover different aspects of URL inspection.

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?

Usage is implied by the purpose — scan a target URL's HTTP security headers — but the description offers no explicit when-to-use guidance or routing against siblings such as check_cors or check_ssl. Nothing is misleading, but the agent must infer selection.

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