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

With no annotations supplied, the description carries the full burden and does disclose a distinctive behavior: it refuses with do_not_answer when data has drifted or is unverified rather than guessing. That is meaningful safety context an agent cannot get from the schema. It stops short of covering auth, rate limits, or the shape of a successful response.

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, front-loaded with the action and followed by the failure behavior; nothing is padded. Minor jargon ('pack', 'do_not_answer') costs a little clarity but not much space.

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 simple one-parameter lookup the description covers refusal behavior, but with no output schema it should describe what a returned 'fact' looks like, and it leaves the fact_id's origin and format entirely unexplained. Adequate but with clear gaps.

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% and the single parameter fact_id has no documentation anywhere. The description never mentions fact_id, its expected format, or where to obtain a valid one, so it fails to compensate for the coverage 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?

The description states a specific verb and resource ('Get one verified fact') and scopes it to the customsuk pack, which lets an agent distinguish it from customsuk_list_facts (plural listing) and customsuk_changes. It does not explicitly name those siblings, so differentiation is inferable rather than stated.

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: 'Get one verified fact' suggests retrieving a single known item by identifier, while listing or change-tracking would use siblings. There is no explicit when-to-use/when-not-to-use guidance and no statement that the fact_id must first come from customsuk_list_facts.

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