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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the description's job is to add context — and it does: it discloses that results pair the current-law value with the not-yet-in-force Omnibus value and include the last-checked date. That dual-value structure is non-obvious behavior an agent would otherwise not anticipate. It stops short of describing response shape or units of the returned sizes.

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?

A single front-loaded sentence that leads with the verb and the returned values before the regulatory citation. The regulatory qualifiers ('as amended by Regulation (EU) 2024/2865', 'section 1.2.1.4 of Annex I') are dense but genuinely load-bearing for a compliance tool, so little is wasted.

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 takes on the burden of explaining what comes back, and it does so by enumerating the three size values plus the Omnibus comparison and last-checked date. Combined with full schema coverage on both parameters, an agent has enough to call it correctly; only units and response field naming are unaddressed.

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%, so the baseline is 3. The phrase 'for a pack size' loosely ties to volume_ml, but the description adds no clarification on unit handling (e.g. litres vs millilitres), boundary behavior at the maximum, or how the optional language parameter affects the returned values.

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 ('Returns') and a concrete, enumerated resource: label size, pictogram size and minimum font size (x-height) for a pack size under a named CLP Annex section. The subject matter is narrow enough that no sibling tool comes close to overlapping, but the description never explicitly differentiates itself from alternatives such as check_gpsr_information or search_knowledge.

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 implied rather than stated: the agent can infer it applies when it needs CLP label dimensions for a given package volume. There is no explicit when-to-use, no when-not-to-use, and no pointer to an alternative source for related compliance questions.

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