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

With no annotations, the description carries the full burden. It discloses the rate limit (20 requests/minute) and the return format ('actual header value and an explanation'). However, it does not specify behaviors like redirect handling, error responses, or whether the fetch is raw or browser-like. This is acceptable but not richly transparent.

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 two sentences and information-dense. The first sentence details the purpose and specific headers, while the second adds usage and rate-limit context. No fluff or redundancy.

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 tool with one parameter, no output schema, and no annotations, the description covers purpose, specific checks, return value details, usage intention, and rate limit. It would be more complete if it mentioned edge-case behavior like redirects or timeouts, but it is sufficiently complete for a simple audit 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?

The input schema already provides 100% coverage for the single parameter 'url', including a description and example. The tool description does not add additional parameter-level semantics beyond what the schema states, so the baseline score 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?

The description clearly states the tool's function: 'Fetch a site and grade its HTTP security headers (A-F)'. It lists the specific headers checked (CSP, HSTS, etc.), distinguishing it from sibling tools like site_status_check or dns_lookup. The verb 'grade' and resource 'HTTP security headers' are specific and unambiguous.

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 description provides clear usage context: 'Use it for a quick security review of your own site or a third party's.' This indicates when the tool is appropriate, but it does not explicitly mention alternatives or when not to use it. Thus it falls short of a 5 but is stronger than a 3.

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