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 contribute real behavior: it discloses the failure path (returns do_not_answer) and the condition (drifted or unverified) rather than guessing. However, 'drifted' is unexplained jargon and there is no disclosure of permissions, output shape, or whether a returned fact is stable/cached.

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 no filler, and the core action is front-loaded ahead of the refusal behavior. Minor deduction for unexplained internal terms like 'pack' and 'do_not_answer' that assume prior context.

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 and no annotations, the description covers purpose and the refusal path but leaves the identifier's origin and the shape of a successful result unstated. Adequate, not complete.

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 exactly one parameter, fact_id, at 0% schema description coverage, so the description must compensate and only partially does — it never states the identifier format or that fact_id comes from benefitsuk_list_facts. Baseline for a single-parameter tool keeps this at 3 rather than lower.

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 from the benefitsuk pack.' The singular 'one fact' implicitly distinguishes it from benefitsuk_list_facts and benefitsuk_changes, though it never names those siblings explicitly.

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 only implied by the phrase 'one verified fact' — an agent can infer this is the single-record lookup versus the list/changes siblings, but there is no explicit when-to-use, no prerequisite, and no statement of where a fact_id is obtained.

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