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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds that the output includes code/name/decimals for crypto and includes fiats, but it does not disclose return shape, ordering, completeness, or whether the data is live or static. With annotations carrying the safety burden, this is adequate but not rich.

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 a single, compact phrase that conveys exactly what the tool returns without filler. Every element—supported assets, code/name/decimals, and fiats—earns its place. It is appropriately minimal for a parameterless lookup tool.

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?

Given zero parameters and no output schema, the description provides enough information for an agent to call the tool and interpret the response at a high level. It mentions the fields included and that both crypto and fiat are covered. It could be more explicit about the response structure, but for such a simple read-only tool it is largely complete.

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 tool has zero parameters, so the input schema covers 100% of the parameter surface trivially. There is nothing for the description to add about parameters. The zero-parameter baseline of 4 applies because no guidance is needed or could be provided.

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 name 'getCurrencies' combined with the description 'Supported crypto assets (code/name/decimals) and fiats' clearly identifies a read operation that returns a list of supported assets and currencies. It distinguishes itself from siblings like getExchangeRates or getBalance by content type, but lacks an explicit verb in the description, so it doesn't quite reach the full 'specific verb+resource' standard.

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 does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions or sibling tools. However, the purpose is simple and self-evident: an agent would use this when it needs the list of supported crypto assets and fiats. This qualifies as implied usage rather than explicit guidance.

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