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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely useful behavior: which rate is applied (banker's selling rate), that results are estimates only, and that on_date selects a historical rate. It stops short of describing rounding, precision, or error behavior.

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?

Three short sentences, front-loaded with the core action and rate type, then the estimate caveat, then the date parameter. No filler or repetition.

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 5-param, no-output-schema read tool, the description covers the essential agent-facing facts: what conversion rate is used, that output is an estimate, and how historical dates work. Missing only minor details like output precision or failure modes for invalid currency codes.

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 all five parameters are already documented with format and examples. The description reinforces on_date semantics (DDMMMYY, past day's rate) but adds little beyond what the schema states, including the 400-day limit. 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?

States a specific verb (converts) and resource (amount between currencies) and pins down the exact rate used ('banker's selling rate'). Siblings are hotel/trip tools, so no direct sibling confusion exists, but the description does not need to differentiate against an alternative converter.

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?

Gives a clear usage caveat: 'For estimates only: hotel bookings are made in the rate's own currency', which tells the agent not to treat the result as a bookable amount. It also explains when on_date matters. It does not name alternatives or exclusions, but none are obviously relevant here.

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