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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds behavioural context beyond that: it discloses the coverage of the dataset (five named sources), that a 'last checked for a newer DVSA file' timestamp is tracked, and that every DVSA file held is listed — non-obvious operational detail.

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 sentence with the core claim (date and age of sources) front-loaded and the source list in parentheses. It is dense but every clause earns its place; the parenthetical enumeration is long but functional rather than 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?

An output schema exists, so return-value structure need not be explained, and the description already characterises the content of that output well. With no parameters and annotations covering risk, the only missing piece is explicit when-to-use guidance relative to siblings.

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 input parameters, so the baseline is 4. The description goes slightly further by describing the semantics of a returned/related value (`release`) as consumed by recent_changes, though it adds no parameter syntax because none exist.

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 the exact resource it reports on (date and age of every source behind HaulierScope) and enumerates the concrete sources, so an agent knows precisely what this tool returns. It does not explicitly contrast itself with siblings, but the resource is specific enough to be distinguishable from get_licence, recent_changes and the other lookup tools.

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?

It supplies a concrete usage hint by stating the DVSA file list is 'usable as `release` in recent_changes', which tells the agent exactly how to chain this tool into a sibling. It stops short of stating when this tool should be preferred over alternatives (e.g. as a freshness pre-check) or any exclusions.

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