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

With no annotations, the description carries the full burden and largely meets it: it discloses that the tool fetches a URL or parses inline JSON, runs checks server-side, needs no browser, and returns a defined JSON shape. It stops short of permission/auth or rate-limit behavior, but for a read-only validator this is strong.

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?

Purpose and the not-use case are front-loaded, which is good, but the description is padded with promotional copy ('84% of teams now using design tokens... every adopting team needs a validator') and a hedged spec-history sentence ('published Oct 28 2025 as a Candidate Recommendation and considered stable') that do not help an agent invoke the tool. Roughly two sentences of pure sales pitch.

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 purpose, usage, exclusion, execution model, and the return shape (checks with id/name/status/detail, valid, score) even though no output schema exists. Nothing an agent needs to select and call this tool correctly is missing.

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 a constraint not present in the schema: 'Pass url to fetch a remote token file, or dtcg_file to validate an inline JSON string. Provide exactly one.' This mutual-exclusivity rule is genuine added meaning beyond the two property descriptions.

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?

Specific verb (Validate) plus a precise resource (design token file) against a named standard (W3C DTCG 2025.10). It explicitly distinguishes itself from the sibling designesy_score by scoping to a token file rather than a whole live site.

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 a positive trigger (verify a tokens.json or any DTCG export is structurally correct) and an explicit exclusion ('When NOT to use: for scoring a whole live site... use designesy_score'). The alternative is named with the condition that selects it.

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