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

Annotations already declare read-only, open-world, non-destructive, but the description adds real value beyond them: output shape and the 20-violation cap, no-auth requirement, and the important epistemic caveat that absence of findings is not evidence of conformance. That caveat is the kind of trust-calibrating context annotations cannot convey.

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?

Four sentences, front-loaded with capability, then output shape, then access condition, then limitations. No filler; each sentence carries distinct information an agent needs.

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 a full output schema present, the description needn't detail return structure, yet it still summarizes it usefully. Combined with the access condition and conformance caveat, an agent has everything needed to call this correctly and interpret results honestly.

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%, so both `url` and `fresh` are already documented, including the cache-bypass semantics. The description only reinforces that any public URL is acceptable and never mentions the caching/fresh behavior, so it adds little beyond the schema. 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?

States a specific verb (scan) plus resource (single web page) and names the exact standard and engines (WCAG 2.2 AA, axe-core, HTML_CodeSniffer, APCA). An agent immediately knows what it does and that it is page-scoped, not site-wide.

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?

"Works for any public URL, no account needed" gives a clear applicability condition, and the caveat about automated testing not establishing conformance tells the agent when the result is insufficient. There are no siblings to differentiate from, and no explicit when-not-to-use beyond that caveat.

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