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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered; the description adds real substance beyond that with the null-before-completion rule, the results_unavailable fallback when stored results cannot be read, and the caveat that absent failing checks do not imply WCAG conformance. It stops short of describing permissions or any partial-failure behavior beyond the one fallback flag.

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 content is front-loaded with the primary return shape, but it is delivered as one dense, run-on enumeration that mixes entity fields, result structure, edge cases, and methodological caveats. Every element is relevant, yet the lack of sentence breaks or ordering makes it harder to scan than it needs to be.

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 return-value burden and does so thoroughly: entity fields, run summary, per-template roll-up with its caps, re-scan fix verification, and the null/unavailable states. The only meaningful gap is how to obtain the required id.

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 0% and the sole parameter is documented only as "by id", with no indication of the uuid format or where the id is obtained (presumably list_accessibility_scans). The description does not compensate for the coverage gap, so an agent must infer the id source.

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 and resource ("Returns one Accessibility Scan by id") and immediately distinguishes itself from the list sibling by emphasizing a single scan retrieved by id. An agent can tell this apart from list_accessibility_scans without opening the 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?

Usage is only implied: "by id" suggests it is a follow-up to listing scans, but the description never names list_accessibility_scans as the source of ids or states when to prefer this over it. No exclusions or prerequisites are given.

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