fx.rates

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

With no annotations, the description adds behavioral context: it indicates a read-only operation returning rates. It lists optional parameters and defaults (e.g., base default USD), but does not mention failure modes, rate limits, or output format details. Sufficient for a simple query but lacking in depth.

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 sentence followed by a concise list of parameters. It is well-structured with the main purpose first and no wasteful words, earning its place efficiently.

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 simple read-only tool with 4 optional parameters and no output schema, the description covers the data source, scope, parameter usage, and defaults. It does not describe the response format but is otherwise complete. Sibling comparisons are absent but not critical here.

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 covers 50% of parameters with descriptions. The overall description adds meaning: it states the default for base (USD), the format for date (YYYY-MM-DD; omit for latest), and explains amount. This compensates for schema gaps and provides usage context.

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 it provides 'Daily reference exchange rates from the European Central Bank (via Frankfurter)' covering '30+ major currencies', which is a specific verb+resource. This differentiates it from sibling tools like 'treasury.exchange-rates' which provide different sources.

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 specifies the data source and scope (ECB, major currencies), implying use for European reference rates. It does not explicitly exclude alternatives or state when not to use, but the context of sibling tools and clear source provides sufficient guidance.

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