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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint. The description adds valuable behavioral context beyond that: the weekend/holiday snapping behavior, the exact return fields (rate, actual date, snap flag), and automatic EUR triangulation. No contradictions with annotations.

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?

Two tightly written sentences with zero filler. The primary purpose is front-loaded, and the return behavior is summarized in one breath. Every clause earns its place.

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 conversion tool with a well-populated schema and an output schema, this description covers all essential behavioral aspects: return values, date snapping, triangulation, and the optional nature of the date parameter. No missing information the agent needs to invoke it 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?

Schema coverage is 100% with rich descriptions for all four parameters, so the schema does the heavy lifting. The description adds negligible parameter-level detail beyond what the schema already provides (e.g., date handling, amount constraints, currency code reference). Baseline 3 is appropriate.

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?

Description states a specific verb-resource pair ('Convert an amount between any two currencies') and differentiates from sibling rate-getters by framing the action as conversion, not just rate retrieval. It also lists what it returns, making the tool's role unambiguous.

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 clearly implies usage for conversions (as opposed to rate-only queries like fx_get_rate) and mentions automatic EUR triangulation, but it does not explicitly name alternatives or state when to prefer this over siblings. The context is sufficient without being explicit about exclusions.

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