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

Annotations already provide readOnlyHint and openWorldHint. The description adds valuable context: it runs exactly 10 checks and returns a score, issues list, and summary. It doesn't cover edge cases like invalid URLs, but for a simple read-only tool this is sufficient.

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, front-loaded with the action and result. The description is extremely compact with zero filler.

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 well-documented parameter, no output schema, and safety annotations, the description is fully complete. It states what it does, what it returns, and when to use it, leaving no important gaps.

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 covers the 'url' parameter with 100% coverage, including the 'must start with http:// or https://' constraint. The description only says 'webpage URL,' which adds no new meaning beyond the schema, so baseline 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 a specific verb+resource: 'Run 10 basic accessibility checks on a webpage URL.' It also specifies distinct outputs (score, issues list, summary), which differentiates it from the many other lookup_* sibling tools like DNS, IP, or WHOIS.

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?

It explicitly says 'Use when you need a quick accessibility audit,' providing a clear use case. It doesn't mention when not to use it or alternatives, but there are no other accessibility tools in the sibling list, so no exclusion is needed.

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