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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and scope are known. The description adds what the output contains ('with what to ask the supplier for') and the empty-input behavior (enumerates product types), which is genuinely useful beyond the annotations. It doesn't mention data freshness or limitations, keeping it just short of a 5.

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 dense sentences with no filler. The trigger leads, the scope is enclosed in parentheses, and the fallback behavior is front-loaded at the end. Every clause carries information.

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 read-only, zero-required-parameter lookup tool without an output schema, the description covers purpose, trigger, scope, output content and default-input behavior. Missing only minor behavioral details such as whether the list is exhaustive or how links are structured, but nothing blocks correct invocation.

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 100%, and the schema already documents both locale and product_type including the zh option and example product types. The description reinforces the no-product_type fallback but adds little syntax not in the schema. Baseline 3 is appropriate.

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 (lists) and resource (UK regulatory regimes) and enumerates the regimes covered (UKCA, WEEE, PSTI, toy safety, food contact, REACH, packaging EPR). Clearly distinguishable from siblings like find_duty_rate or check_import_rules which cover tariffs or China-side rules.

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?

Opens with an explicit trigger: 'Use when the user asks which UK rules, markings or certificates a product imported from China needs.' It also documents the no-argument fallback (lists product types). It lacks explicit exclusions or named alternatives, but the trigger condition is clear.

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