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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: it is static and versioned, so results are stable and cacheable, and it discloses that conventions for tiers, delays, timestamps, and missing-data reporting are documented inside.

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?

Two dense sentences, front-loaded with what the guide contains and closed with the operational facts (no inputs, static per version). Every clause carries information; there is no filler.

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 convey the return content, and it does so by listing the categories (unit, value set, meaning, shared response conventions). It stops short of describing the guide's organization/lookup structure, which would fully close the loop for a reference 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?

There are zero parameters, so the baseline is 4. The description correctly confirms this by stating 'No inputs', leaving no ambiguity about whether arguments should be supplied.

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 names a specific resource (a static, versioned field dictionary for this surface) and enumerates exactly what it contains: units, value sets, one-sentence meanings, and shared response conventions. It also states that it takes no inputs and is static per version, which makes it immediately distinguishable from the data-fetching siblings.

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?

Usage is only implied: an agent can infer this is the lookup table for interpreting fields emitted by the sibling tools, but the description never says when to consult it (e.g. before parsing other tool output) or when it is unnecessary. No alternative or exclusion is named.

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