fx

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

With no annotations provided, the description carries full burden and excels: it discloses cost ($0.002 per call), data source (ECB via Frankfurter API), update frequency (once per business day, 16:00 CET), caching (up to 1 hour), and scope (daily reference rate, not live).

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 concise (roughly 100 words), front-loaded with critical info (cost and purpose), and well-structured. Every sentence adds value without redundancy.

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 no output schema, the description covers key aspects: input format, data source, update cadence, caching, cost, and typical use cases. It is sufficiently complete for an agent to use correctly.

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 schema has 100% parameter description coverage (each param gets a clear description). The description adds marginal value: it notes ISO 4217 codes and mentions ~30 major currencies, but the schema already specifies the pattern and example.

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 states the tool retrieves 'the ECB reference exchange rate between two fiat currencies,' which is a specific verb+resource. It distinguishes itself from sibling tools like crypto_price and defi_tvl by focusing on fiat currencies via official ECB rates.

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 provides explicit use cases ('currency conversion, pricing normalization, and financial reporting by agents') and clarifies it's not a live trading feed. However, it does not explicitly state when not to use this tool or compare it to alternatives.

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