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

With no annotations present, the description carries the full behavioral burden and does disclose a meaningful trait: the tool refuses with a do_not_answer signal on drifted or unverified data rather than guessing. That is genuinely useful, but it omits what a refusal actually looks like in the response, whether any auth or rate limits apply, and whether retrieved facts are cached or versioned.

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 core action and followed by the failure contract — nothing wasted. Minor jargon ('pack') and the parenthetical token add slight noise without blocking comprehension.

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 the core action and the refusal behavior, but it never describes the successful return value and never explains how to source a fact_id. An agent could call it only after guessing the identifier format.

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 required parameter, fact_id, with 0% schema description coverage, so the description is the only place its meaning could be established. It says nothing about the format of fact_id or where an agent should obtain one (presumably from the list tool), leaving the sole input undocumented in both schema and prose.

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: retrieve a single verified fact from the passportuk pack. The singular 'one fact' implicitly separates it from the listing sibling (passportuk_list_facts), but the description never names that alternative, so the differentiation is inferred 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?

The description implies the usage mode (single-fact lookup) and adds an important contract about when the tool will refuse to answer, but it gives no explicit routing guidance — it never says to use passportuk_list_facts first to discover IDs or passportuk_changes to check for updates.

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