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

The readOnlyHint and destructiveHint annotations already cover the tool's safety profile, so the description does not need to restate it. It adds only scope ('fiat'), but no behavior beyond what the annotations imply; this is acceptable for a trivial list endpoint.

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?

A single front-loaded sentence containing only the essential verb and object. There is no filler, and for a zero-required-parameter list tool this is an ideal length.

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, zero-required-parameter list operation, the description is nearly complete: an agent knows what it does and that no input is needed. It could mention the return shape (e.g., an array of currency codes) since no output schema exists, but 'List' makes the expected result clear.

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 only parameter is an optional raw JSON passthrough that the schema already describes at 100% coverage. The description adds no parameter detail, but none is needed because no required or typed parameters exist.

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?

Describes a concrete operation ('List') on a specific resource ('supported fiat currencies'), which is immediately useful. It does not explicitly distinguish this from sibling peer_market_meta_currencies, though the word 'fiat' narrows the scope.

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 intended use is inferable: call when you need the configured fiat currency list. However, the description gives no guidance on when to prefer this over related config/market metadata tools, nor any exclusions.

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