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

readOnlyHint=true already covers the safety profile, lowering the bar. The description adds meaningful context beyond the annotation: the 'public website' constraint sets the expectation that non-public or internal sites are out of scope, and it summarizes the analytical nature of the operation and its return payload. It doesn't disclose rate limits or runtime, but for a read-only scanner these are minor gaps.

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?

Two sentences with zero filler. The first sentence front-loads the verb and resource, then enumerates the output; the second sentence gives the usage trigger. Every clause 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?

Single required parameter documented at 100%, output schema present to cover return values, annotation covers the read-only safety profile, and the description covers purpose plus the exact trigger condition. There is nothing an agent needs to invoke this tool correctly that 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 description coverage is 100% — the url parameter is fully documented in the schema ('Public http(s) address, for example example.com'). The description adds only the word 'website', which marginally reinforces that the URL should point to a site rather than a generic resource. With full schema coverage, baseline 3 is correct.

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 ('Score'), a concrete resource ('a public website for agent readiness'), and enumerates the exact output payload (0-100 score, grade, fitness/adoption sub-scores, highest-value fixes). The phrase 'Use this first' plus the return-payload detail clearly distinguishes it from siblings like explain_check, list_checks, and watch_site within the same domain.

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 an explicit trigger: 'Use this first when asked whether a site is agent-ready or WebMCP-ready.' This is clear context for when to select the tool. It stops short of naming the sibling alternatives or stating when-not-to-use, so it doesn't reach full routing explicitness.

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