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

With no annotations, the description carries the full burden and does so well: it discloses that execution is server-side, that CSS is extracted from inline and linked stylesheets, that :root custom properties and var() references are parsed, that no browser is needed, and that results are cached ~24h. It does not mention authentication or rate limits, but the behavioral surface is otherwise well covered.

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?

Front-loads the purpose, then checks, then usage routing, then execution mechanics, then return shape, then caching. Sentences are information-dense and every one earns its place, including the specific parentheticals defining each failure mode.

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?

Covers everything an agent needs despite having no output schema: it inlines the full return JSON shape (score, grade, pass/warn/fail, checks array), explains execution semantics, and notes the 24h cache. Complete for a single-param scoring tool.

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% and the single url param (with its default) is already fully documented in the schema. The description adds no syntax or format detail beyond it, so the 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+resource+scope ('Score a live URL for AI-generated UI drift') and immediately enumerates the 12 checks and the four failure modes it detects. It explicitly names the siblings it is not (designesy_score, designesy_tokens_score), so an agent can route without opening any 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?

Gives an explicit when-to-use condition ('verify whether a site is drifting off its own declared token system') and a when-NOT-to-use block that names two alternatives with the exact conditions selecting them (full 42-check contract vs token-file format validation). Nothing is left to inference.

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