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

With no annotations supplied, the description carries the full behavior burden and does disclose the most important trait: the tool returns a do_not_answer refusal rather than guessing when the fact has drifted or is unverified. That is genuine, non-obvious behavioral context an agent needs in order to handle the response. It does not describe the success response shape or how a refusal is surfaced, which keeps it below 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 short sentences, no filler, and the core action is stated first with the refusal caveat second. Every clause carries information the agent could act on.

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?

For a one-parameter read tool with no output schema, the description covers purpose and the key failure mode, which is most of what is needed. It leaves the fact_id contract and the success return value unaddressed, so an agent still has to guess at how to source a valid ID.

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 0% for the single parameter, so the schema says nothing about fact_id beyond its type being string. The description does not compensate at all: it never states the identifier format, where to obtain it, or whether it is a slug, key, or opaque ID. For a lookup tool the identifier is the whole call contract, so this is a meaningful gap.

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?

"Get one verified fact from the vehicleuk pack" gives a specific verb (get), a specific cardinality (one), and a named domain (vehicleuk), which implicitly distinguishes it from vehicleuk_list_facts and vehicleuk_changes that appear in the sibling list. It stops short of naming those siblings explicitly, so the differentiation relies on the agent noticing the list/get prefix pattern rather than being told.

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?

The description implies usage for retrieving a single fact by identifier, and adds a negative condition (it refuses when data is drifted or unverified). It never says where a valid fact_id comes from (presumably vehicleuk_list_facts) or when to prefer the list or changes tools instead, so the routing guidance is only implied.

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