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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety and caching profile is covered. The description adds two genuinely useful facts beyond that — 150+ currency coverage and daily rate updates (data freshness) — but says nothing about rate type, latency, or rate limits.

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 sentences, well front-loaded, but the second sentence largely duplicates the first ('converting an amount between currencies') and adds only the vague 'exchange rates' use case. Roughly half the text does not earn its place.

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?

An output schema exists, so return-value explanation is unnecessary, and annotations carry the safety profile while the schema carries full parameter detail. What remains — purpose, currency coverage, and update cadence — is present, leaving only minor gaps around rate semantics.

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 all four parameters, including the enum-rich locale field with its per-call instruction, are documented in the schema itself. The description contributes no parameter-level meaning, so the baseline of 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 states a specific verb and resource: converting an amount between two currencies, and adds live-rate scope (150+ currencies, daily updates). It doesn't differentiate from siblings because no sibling operates on currency, so nothing further is needed.

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 second sentence, 'Use it for exchange rates and converting an amount between currencies,' is a restatement of the purpose rather than conditional guidance. No when-not-to-use, no prerequisites, and no alternative tool is named — though the sibling list contains no competing currency tool.

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