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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, covering the safety profile. The description adds only the ECB source and date format requirement, which are useful but not rich behavioral disclosures. It does not contradict any 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 short, focused sentences. The first states the core function; the second gives the date format. No redundancy or filler.

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?

The tool is simple, annotations cover safety, an output schema exists, and parameters are fully described. The description supplies purpose, source, and format, which is complete for this context.

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 detailed descriptions for both 'date' and 'pair', including a pattern and enum. The description reinforces the date format but adds no meaningful parameter semantics beyond what the schema already provides, so baseline 3 applies.

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 states the tool 'Returns the exchange rate for a G10 currency pair on a specific date,' using a specific verb and resource. It distinguishes from sibling tools like get_fx_rate_current and get_fx_rate_series by emphasizing the specific date, and adds the data source (ECB).

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 explicitly specifies the date-specific use case and instructs 'Use YYYY-MM-DD format,' which is direct guidance. It does not name alternative tools like get_fx_rate_current or get_fx_rate_series, but the qualifier 'on a specific date' clearly implies the intended context.

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