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

Annotations already cover safety (readOnlyHint, destructiveHint, idempotentHint, openWorldHint). The description adds useful operational context: a free daily allowance followed by $0.002 USDC per call via x402, and it characterizes the return as including indents and declarability. This goes beyond the structured annotations, though it doesn't detail authentication or rate-limit mechanics.

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 tight sentences: the first defines the output, the second covers pricing. Both are front-loaded and free of filler, so every sentence earns its place.

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 lookup with a rich output schema and detailed annotations, the description covers the returned data and the payment model. The main omission is routing guidance relative to sibling tariff tools, which prevents a perfect score.

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 single 'code' parameter is documented with type and example. The description repeats '4-digit heading' but adds no syntax, format, or validation detail beyond what the schema provides, so baseline 3 applies.

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 resource ('A 4-digit heading and every commodity code under it') and what it returns ('with indents and whether each is declarable'). It does not name or differentiate from sibling tariff tools like uk-trade-tariff__commodity or uk-trade-tariff__search, so it stops short of a 5.

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 guidance on when to use this tool versus alternatives such as uk-trade-tariff__commodity or uk-trade-tariff__search. The pricing sentence describes cost, not usage context, so the agent is left to infer selection.

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