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 genuinely non-obvious contract: the tool returns a 'do_not_answer' refusal for drifted or unverified facts and never fabricates. That tells the agent to handle a refusal outcome. It stops short of covering unknown-fact_id errors, lookup cost, or what a returned fact contains.

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 compact sentences, front-loaded with the action and followed by the critical refusal caveat. No filler or restatement of the tool name.

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?

A simple one-parameter tool, and the refusal semantics are well covered. But with no output schema, the description should say something about what a fact looks like or how a do_not_answer result is surfaced, and it leaves the fact_id parameter entirely unexplained.

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% for the single required parameter fact_id, so the description needed to compensate and does not. It never mentions the parameter, its expected format, or how to obtain a valid 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 from the energyuk pack.' The singular 'one' distinguishes it from the sibling energyuk_list_facts and energyuk_changes tools by implication, though no sibling is named 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?

No when-to-use guidance beyond the implied single-fact lookup. It never says to call energyuk_list_facts first to obtain a valid fact_id, nor when energyuk_changes would be the better choice for freshness questions. The refusal clause describes behavior, not selection criteria.

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