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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds meaningful context by stating that the output is reference data only, and mentions a 'home-check rule'. No contradiction with the annotations.

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?

The description is two sentences: the first front-loads the resource and enumerates its content, the second is a critical exclusion. Every part earns its place; no filler.

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?

With an output schema present and annotations covering safety, the description is nearly complete: it covers scope, examples, output attributes, and the pricing boundary. The 'home-check rule' is mentioned but not defined, but that detail is likely contained in the output schema.

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?

The input schema covers 'nom' and 'metal' descriptions; the description supplements this with a large set of accepted coin names/aliases and the attribute list. It does not elaborate on 'langue', but the enum covers that parameter adequately.

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 leads with a specific verb and object: 'Reference specifications of common gold and silver coins', and immediately enumerates the attributes (gross weight, fineness, fine metal, diameter, thickness, years). It also distinguishes itself from the pricing tool by adding 'Never a price: use cotation.'

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 description explicitly states when not to use it ('Never a price') and routes the agent to the correct sibling ('use cotation'). Although other siblings exist, the key alternative for this reference tool is clearly named.

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