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

With no annotations, the description carries the full burden, and it does disclose one genuinely useful trait: the tool returns a do_not_answer refusal for drifted or unverified facts rather than guessing. It says nothing about the shape of a successful response, latency, or what a caller should do after a refusal, which leaves meaningful behavioral gaps.

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 tight sentences with the refusal guarantee front-loaded after the core action; nothing is wasted. "Never guesses" is mildly redundant with the preceding clause but reinforces a key trust property.

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 single-parameter lookup with no output schema, the description covers the failure mode well, which is the main risk. It still leaves the agent without any way to know what a valid fact_id looks like or which sibling to call to enumerate them, which is a real gap for a lookup 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 is one parameter at 0% schema description coverage, so the description must compensate for fact_id and does not — no format, no example, no pointer to how fact_ids are obtained. The agent learns only that a fact_id is required.

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 and resource ("Get one verified fact") and scopes it to the holidayuk pack, so an agent can tell it apart from the many sibling *uk_get_fact tools by domain. The word "one" implicitly contrasts with holidayuk_list_facts, but that sibling is never named.

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: call it when you need a single holidayuk fact. The refusal condition ("when drifted or unverified") is behavioral guidance but not a when-to-use-vs-alternative rule, and no sibling such as holidayuk_list_facts is offered as the way to discover fact_ids.

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