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

No annotations are provided, so the description carries the full behavioral burden. It mentions “PRO” and “Latest” but does not state auth requirements clearly (access_token is optional in the schema), rate limits, refresh cadence, or whether the operation is strictly read-only.

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 two short fragments with no wasted words. “PRO” and the currency scope are front-loaded and directly relevant to the tool's purpose.

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 one-parameter read tool this is minimally adequate: it identifies the data and currency set, and the parameter is fully covered by the schema. However, with no annotations and no output schema, it should do more to explain authentication and what the returned rates table looks like.

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 description coverage is 100%, and the single optional access_token parameter is already fully documented in the schema. The description adds no parameter-level semantics beyond what is structured, so the baseline of 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?

States the specific resource (latest JPY rates) and enumerates the currencies covered, so an agent can tell what data is returned. It does not explicitly clarify how this differs from the sibling fx_rate or convert tools, but the plural/table framing is reasonably distinct.

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?

Provides no guidance on when to use fx_table instead of fx_rate or convert. The only usage-related signal is “PRO,” which hints at subscription gating but does not explain selection criteria or alternatives.

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