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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real value beyond that by naming the data domain (UK van database) and enumerating the returned attributes, which matters since there is no output schema. It does not state failure behavior for unknown slugs, keeping it short of a 5.

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 sentences, zero filler: the first front-loads what the tool returns, the second tells the agent how to supply the parameter. The field list is dense but each item is substantive rather than verbose.

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 one required parameter, read-only annotations, and no output schema, the description carries the full burden of describing return content — and it does so by naming the spec categories. Nothing an agent needs in order to select and call this tool 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 supplies a slug example, so the baseline would be 3. The description earns one extra point by specifying the slug's provenance ('from search_vans'), signaling that the value must come from a prior search rather than being invented.

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 states a specific resource ('one van version in THRIVE's UK van database') with an explicit enumeration of what the specification contains (price, grant, payload, gross weight, load dimensions, power, economy or range, battery, charging). This makes it immediately distinguishable from search_vans, which only locates vans rather than returning full specs.

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?

'Pass the slug from search_vans' establishes the correct workflow: search first, then fetch details here, which is the key routing decision for an agent. There are no explicit when-not conditions or mention of what happens with a stale/invalid slug, but for a single-record lookup tool the usage context is clear enough.

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