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

With no annotations, the description does carry some behavioral weight: it discloses that the tool refuses with a 'do_not_answer' outcome when data is drifted or unverified rather than guessing. It does not say what an invalid or unknown fact_id returns, nor what a successful fact looks like, and with no output schema those gaps remain.

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 pack scope, and the refusal clause is compact and worth including. Nothing is padded, though the syntax is slightly compressed.

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?

The tool has one required parameter, no annotations, and no output schema, so the description must compensate — but it never explains the identifier or the return shape, and 'do_not_answer' is named without saying how it surfaces in the response. An agent can call it, but cannot predict what comes back or how to recover from a refusal.

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 0% and the only parameter, fact_id, is never mentioned in the description — no format, no example, no statement of where to obtain one. For a single-parameter tool the schema still conveys the type, but the description adds no meaning at all about the identifier.

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') scoped to the marriageuk pack, which distinguishes it from the other *uk_get_fact siblings. It does not distinguish it from the closer siblings marriageuk_list_facts or marriageuk_changes, so the boundary is only implicit.

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?

There is no explicit when-to-use or when-not-to-use guidance and no pointer to marriageuk_list_facts as the way to obtain a fact_id, nor to marriageuk_changes for change history. The refusal condition is a guardrail, not usage guidance.

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