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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond by disclosing the operational model (nightly re-measurement of most-referenced products from live DOM, dated ledger) and what each verdict means, including the do_not_hardcode signal. That is substantial behavioral context the annotations cannot convey.

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 core question, then uses a tight bulleted breakdown of the three verdicts, so each sentence earns its place. Minor marketing flourish ('what a screenshot never can') and the trailing 'Free.' are slight padding but do not obscure the content.

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 must explain the return values, and the verdict taxonomy (held/shifted/unstable plus do_not_hardcode) does the heavy lifting. It is complete enough to call correctly, though the broader ledger/before-after payload shape is only sketched rather than fully described.

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?

With 0% schema description coverage the description must carry the single parameter, and it does: it specifies the format ('bare domain, no scheme') and supplies concrete examples ('stripe.com', 'linear.app'). This meaningfully compensates for the empty schema, though it stops short of adding further constraints.

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 question it answers ('Has this product's design system CHANGED since it was decoded — and which of its numbers are safe to hard-code') with a clear verb+resource, and explicitly differentiates from the sibling: 'get_design_system(site) gives the spec, this gives its shelf life.' An agent can pick it apart from the other design tools 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?

Gives clear when-to-use instructions ('Call this BEFORE building against a cached spec, and before baking any measured value into a token file') and names its complementary sibling. It omits any explicit when-not-to-use or exclusions, which keeps it from a full 5, but the routing guidance is strong.

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