Get VAT Rate for Commodity

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

Annotations already declare readOnlyHint and idempotentHint, so description is not burdened with safety disclosure. The description adds behavioral context: uses a static lookup table dated 22 Nov 2023 and that rates may have changed, which is critical for correct agent behavior. Minor gap: no mention of error handling or no-match case, but overall strong.

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?

Three concise sentences: first is a clear directive with usage, second details output, third provides crucial caveat and alternative. Perfectly front-loaded and no wasted words.

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 one-parameter lookup tool with output schema, the description fully covers purpose, usage, output, staleness caveat, and alternative. The presence of an output schema complements the return value details. Nothing essential is missing.

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?

Input schema covers the single parameter with description and examples (100% coverage). Description does not add significant new meaning beyond what the schema already provides; it restates the purpose but does not clarify edge cases or format further.

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?

Description starts with 'USE THIS TOOL WHEN' explicitly stating the tool's purpose: getting VAT rate for a UK commodity/service. It lists returned rate categories (standard, reduced, zero, exempt) and distinguishes from sibling hmrc_search_guidance for up-to-date advice.

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?

Explicitly states when to use (having a UK commodity/service description) and, importantly, when not to use (time-sensitive advice) by directing to hmrc_search_guidance. Provides clear exclusion and alternative.

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