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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is fully covered. The description adds meaningful provenance context ('cross rates computed from a USD table', 'not a transaction rate'), which is more than the annotations provide, but says nothing about caching, rate limits, or freshness of the rates.

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?

Short, front-loaded, and every clause adds information (provenance, caveat, defaults). The trailing bilingual '(참고용 환율)' slightly duplicates the English caveat but is negligible overhead.

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 two-param, zero-required read tool with rich annotations and no output schema, the description covers what it does, its precision caveat, and its default behavior. Only the return shape/freshness is unstated, which is minor at this complexity.

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%, so both params are already documented with their defaults in the schema. The description's 'Defaults to 10 major currencies' loosely reinforces the symbols parameter but adds no syntax or format detail beyond the schema.

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?

States a specific resource (exchange rates) and clarifies the nature of the data (cross rates computed from a USD table). This cleanly separates it from the sibling travel/hotel/place tools, which cover entirely different domains, though it doesn't name any sibling explicitly.

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 caveat 'Not a transaction rate' implies reference-only usage, and 'Defaults to 10 major currencies' hints at default behavior. However, there is no explicit when-to-use guidance, no prerequisites, and no mention of alternatives for transaction-grade rates.

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