get_rates

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

With no annotations, the description must carry behavioral disclosure, and it does: it reveals the response is an array with one row per target×time bucket, defines the shape [{ rate, source, target, time }], and implies the operation is read-only. It does not cover potential rate limits or error behavior, but those are secondary for a straightforward retrieval tool.

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?

Every sentence carries information: use cases, output shape, and routing to siblings. It is front-loaded with the most important selection criteria and contains no filler or repetition of schema text.

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 six-parameter tool with no output schema, the description covers the core usage modes, mutual exclusivity of parameters, grouping behavior, and response cardinality. It could also state ordering or time format of returned rows, but enough is present for an agent to call the tool correctly in the main scenarios.

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 already documents all six parameters at 100% coverage, so the baseline is 3. The description adds meaningful semantics on top: it links the target multiplicity to row count, explains the output row format, and frames parameters in concrete usage scenarios like 'USD vs EUR, GBP, JPY'.

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 names a specific verb ('get rates') and enumerates three distinct use cases with concrete examples: multi-target queries, point-in-time rates, and custom date ranges. It also distinguishes itself from siblings by explicitly covering what this tool is for, rather than restating the tool's name.

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?

Usage guidance is explicit and actionable: single live pairs should use get_exchange_rate, and fixed lookback windows should use get_historical_rates. It also references list_currencies for code validation, giving clear when-to-use and when-not-to-use direction.

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