List supported currencies

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

With no annotations, the description carries the full burden and does well: it discloses that no API key is needed, that the default response is a compact code → name map, which fields detailed=true adds (country, status AVAILABLE/DEPRECATED, availableFrom/availableUntil), and warns that the full detailed catalogue is very large. Gaps are minor — nothing on rate limits, error behavior, or pagination of the 1000+ item list.

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?

Front-loaded with what the tool returns, then usage, then auth, then the two parameter behaviors in progression. Four dense sentences with no filler and no repetition of the schema text verbatim.

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 2-parameter, no-annotation, no-output-schema read tool, the description covers the essentials: return shape in both modes, auth requirement, catalogue size caveat, and how the parameters interact. Nothing an agent needs in order to call this correctly 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?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning beyond it: concrete search examples ('rupee', 'PK', 'bitcoin') and the behavioral distinction that country names are only matched when detailed=true. That extra context lifts it above baseline.

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?

States a specific verb and resource ('Returns the currencies supported by CurrencyFreaks') and quantifies the scope: 1000+ fiat currencies, cryptocurrencies, and precious metals with named examples (XAU, XAG, XPT, XPD). It also positions itself against siblings by saying it's used to find a currency code before calling rate or conversion tools, so an agent can distinguish it from get_latest_rates and convert_currency without opening the schema.

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 names the downstream tools (rate or conversion tools) and the condition that selects this one — locating a currency code first. It also gives usage routing between the plain call, 'search', and detailed=true, including the instruction to combine search with detailed because the full catalogue is very large.

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