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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so safety is covered. The description adds meaningful behavioral context: rates are mid-market and refreshed several times a day, and Gulf currencies are pegged with fixed examples. It does not discuss rate source caveats or precision, but the added freshness and peg behavior go beyond the 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?

The description is only three short sentences plus a URL, and each sentence contributes something (peg example, core purpose plus rate freshness, source link). It is slightly back-loaded, with the core purpose appearing after the example, but it remains efficient and free of 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?

This is a simple read-only calculator with no output schema needing explanation, and annotations cover the safety profile. The description supplies the essential facts: what it converts, how many currencies, rate type, refresh cadence, and a documentation link. Missing only minor details like rounding behavior or whether rates are indicative, so it is nearly complete.

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%, with enums for from/to and a numeric amount field bounded at 0 to 1e15. The description does not add meaning beyond the schema — e.g., it doesn't explain rounding, default behavior, or how the amount is interpreted. Baseline 3 is appropriate when the schema fully documents parameters.

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 second sentence clearly states a specific verb and resource: convert 39 currencies at mid-market rates. That inherently distinguishes it from unit, cooking, or fuel-economy converters in the sibling list, though no alternative is named explicitly. The first sentence about Gulf pegs is a concrete example that reinforces the fixed-rate behavior rather than clouding the purpose.

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?

Usage is implied by 'Convert 39 currencies' — an agent can infer this is for currency exchange calculations. However, the description does not say when to choose this over a sibling like unit_converter, nor does it state any exclusions or prerequisites. No explicit when/when-not guidance is provided.

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