Check that every file the site points at exists

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

Annotations already declare readOnlyHint and idempotentHint, and the description goes well beyond them by revealing specific behaviors: it reports file:line for missing assets, deliberately catches macOS-vs-Linux case-sensitivity failures, and treats CSS custom properties as references. This is exactly the kind of non-obvious behavioral context that helps an agent predict side effects and limitations.

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 front-loaded with the core behavior in the first sentence, then adds two high-value edge cases. Every sentence earns its place: none restate the tool name or repeat schema details, and the length is appropriate for the complexity.

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?

Given the output schema, full parameter documentation, and read-only annotations, the description closes the important gaps: asset scope, reporting format, the platform-specific failure mode, and the theme-contract nuance. An agent has everything needed to decide to invoke it and what to expect.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning to the check_theme parameter by explaining that var(--token) is a reference and that a custom property defined only inside a dark-mode media query has no value in the default state. It also clarifies the internal-link scope covered by check_links.

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 opens with a specific verb and resource: 'Follows every image, stylesheet, script, icon and internal link... and confirms the file is really there.' It also states the concrete output ('Reports file:line'), which clearly differentiates it from the sibling check tools like check_copy or check_responsive.

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 gives a clear context for when this tool matters, especially the case-sensitivity trap that cannot be caught on the building Mac. It does not explicitly name sibling alternatives or say 'use this instead of X', but the scope is specific enough that an agent can recognize it as the asset-existence check among the sibling tools.

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