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

Annotations already declare readOnly, idempotent, non-destructive. The description adds real context beyond that: the rate type (banker's selling), the estimate-only caveat, and that hotel bookings are made in the rate's own currency – a crucial behavioral insight.

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 sentences front-load the core action and rate type. The second sentence adds a critical caveat and a param hint without padding, though the param hint could be slightly reorganized.

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?

With no output schema or annotations for safety, the description adequately covers rate type, estimate nature, and on_date semantics. It doesn't explain via_nation or to_currency defaults, but the schema does that partially; overall sufficient for a read-only conversion tool.

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 baseline is 3. The description adds meaning for on_date (DDMMMYY selects a past day's rate) and explains the estimate-vs-booking currency caveat, going beyond schema descriptions.

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 verb+resource ('Converts an amount between currencies') and adds scope: the banker's selling rate. Among siblings (hotel/trip tools) this is clearly the only currency tool, so differentiation is inherent.

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?

No explicit when-to-use or alternatives are named, but the description implies usage by framing results as estimates for hotel bookings. This is implied rather than stated guidance.

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