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

With no annotations provided, the description carries the transparency burden. It discloses meaningful behavior: multi-source cross-referencing (ECB/台銀) and output containing same-day plus 1-week/1-month/3-month changes. It does not detail update frequency or exact output shape, but these are non-critical for a read-only spot-rate 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?

The description is short, front-loaded with the core purpose, and packs sources and time periods efficiently. The English sentence mostly repeats the Chinese content, creating minor redundancy, but it does not waste much space.

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 single-optional-parameter tool with full schema coverage, the description is reasonably complete: it tells the agent what the tool returns and that a pair can be specified. The lack of an output schema is partly compensated by describing the included time-period changes. Missing guidance on sibling selection is the main gap.

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%, so the pair parameter is already documented in the schema. The description adds a concrete example (USD/TWD) but no additional semantic detail beyond what the schema already states, 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?

The description clearly identifies the resource as spot FX rates for major currencies, with multi-period changes and optional pair specification. It does not use a strong verb like 'retrieve' or 'get', and it does not explicitly contrast itself with sibling tools, so it falls just short of a 5.

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 intended use is implied by 'Spot FX rates' and the optional pair parameter, so an agent can infer this is for currency rate lookups. However, it does not state when to prefer this over sibling tools such as data_point, fetch, or market_sentiment, nor does it give any exclusion criteria.

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