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

The annotations already declare the tool read-only, idempotent, and non-destructive, so the description carries little safety burden. It adds useful context by describing the kind of output (meaning, penalty band, grounds) and includes the caveat 'usually beat it,' implying legal guidance is not absolute. It does not disclose other behavioral traits like data sources or limitations.

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?

One compact sentence that front-loads the main purpose and then lists the key deliverables. Every element adds value, and there is no filler, repetition, or unnecessary detail.

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 lookup tool with a single required parameter and helpful annotations, the description is nearly complete: it tells the agent what the tool returns and the type of input expected. It does not explain how this differs from search_contravention_codes or whether codes outside the listed set are accepted, but these are minor gaps given the simple scope.

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 parameter code is already described with examples in the schema. The description adds the notion of a 'council PCN' and examples of penalty codes, but those largely overlap with the parameter description. It provides no additional formatting or normalization guidance beyond what is in the schema.

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 clearly identifies the resource (council PCN contravention codes) and what the tool provides: meaning, penalty band, and grounds. It lacks an explicit verb in the description text, but the tool title 'Explain a PCN contravention code' supplies it, and the scope is specific enough to distinguish it from a generic search tool.

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 use case is implied: an agent would call this when the user wants to know what a code means or how to challenge it. However, there is no explicit guidance contrasting it with sibling tools like search_contravention_codes, and no stated conditions for when not to use it.

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