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

Annotations already cover the safety profile (readOnly, idempotent, not destructive), and the description adds substantial extra context: the distinction between `updated` (rebuild time) and `vintage` (what the figures describe), with concrete examples showing they can be years apart. It also discloses fetched-vs-reviewed provenance, that no figures or attribution block are returned, and that the tool is pure with `since` supplied by the caller.

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 resource definition and then the updated/vintage semantics, which is the right order. It is dense and occasionally repetitive (the capitalized 'THE TWO ARE DIFFERENT' plus two examples restates the same point), but nearly every sentence carries distinct information.

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 an output schema present and annotations covering safety, the description only needs to explain the non-obvious semantics — and it does: vintage vs updated, sourcing mode, scope, and the meaning of `since`. Nothing an agent needs to call this 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% and the schema already states the strict-after semantics, so the baseline is 3. The description goes beyond by framing the parameter's purpose (cache invalidation / targeted re-fetch) and emphasizing the strict inequality, adding decision-relevant meaning.

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?

Names a concrete resource ('the registry of every dataset behind the site's figures') and enumerates the domain it covers, immediately distinguishing it from the sibling tools that serve figures rather than metadata about them. An agent can tell this is the inventory tool, not a data-serving tool.

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?

States a clear usage scenario: an agent that cached a figure can pass `since` to decide what to re-fetch rather than re-fetching everything. It also gives guidance on judging currency (prefer `vintage`, fall back to `updated`). It does not name a sibling alternative or explicit when-not-to-use, so it stops short of 5.

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