get_currency_rate

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

With no annotations, the description carries the transparency burden. It discloses a meaningful behavioral detail: 'Tries Table A first and falls back to Table B for exotic currencies.' This explains why different currencies may be resolved via different NBP tables. It does not cover failure modes or error handling, but the disclosed fallback logic adds important context beyond the schema.

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 front-loaded with the primary function in the first sentence, followed by a compact and clear Args block. There is no fluff, and every sentence adds value.

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?

The tool is simple (2 parameters, 1 required), and the description covers the data source (NBP), the currency pair (vs PLN), the fallback behavior, and parameter formats. Since an output schema exists, return value details are not needed. Minor gaps like error cases are not covered, but the core usage is fully specified.

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 no descriptions for its parameters (0% coverage). The description compensates fully by defining currency_code as an ISO 4217 code with examples ('EUR', 'USD', 'GBP') and date as an optional ISO date (YYYY-MM-DD) for historical rates, providing formats and semantics beyond the raw field names.

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's function: 'Get the official NBP mid-market exchange rate for a single currency against PLN.' It uses a specific verb and resource, and the phrase 'single currency' differentiates it from the sibling tool 'get_all_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 indicates the tool is specifically for retrieving a single exchange rate against PLN and optionally for historical dates. It provides clear context but does not explicitly rule out alternatives like 'convert_currency' or state when not to use it, though the single-currency framing implicitly guides selection.

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