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

Annotations already establish that the operation is read-only, idempotent, and non-destructive, so the description does not need to restate that. It adds the useful detail that conversion uses the 'most recent reference rate' rather than a custom or historical rate, but it does not disclose output shape, rounding behavior, or rate-source limitations.

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?

A single sentence that front-loads the action ('Convert an amount') and the key scope ('most recent reference rate'). There is no filler, redundancy, or irrelevant context.

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 simple three-parameter read-only conversion with rich annotations, the description is nearly complete: it states the action, the present-time scope, and the parameters are self-evident from the schema. The only missing piece is an explicit return-shape hint since there is no output schema, though the converted amount is strongly implied by the tool's purpose.

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?

The schema documents currency codes for from_currency and to_currency but leaves amount as just a number. The description does not fill that gap: it neither defines amount as a positive decimal in the source currency nor explains precision or minimums. It adds essentially no parameter meaning beyond what the schema already provides.

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 uses a specific verb ('Convert') and names the exact operation: an amount between two currencies, scoped to the most recent reference rate. This clearly distinguishes it from historical/timeseries fx siblings. An agent can identify what this tool does without opening sibling definitions.

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 phrase 'most recent reference rate' implies this is for current conversions rather than historical analysis. However, it never explicitly names alternatives such as fx_historical or fx_timeseries, nor does it state when not to use this tool. The agent must infer routing from sibling tool names.

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