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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuinely new context the annotations do not carry: the rate source is live and refreshed daily, and coverage spans 150+ currencies. It does not say what is returned (converted amount, rate, timestamp) or whether rates are indicative.

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 between two currencies') and appends scope qualifiers. No filler or repetition of the title.

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 tool with full schema coverage and complete annotations, the description covers the essentials plus rate freshness. The one gap is that no output schema exists, so the shape of the result (amount, rate, date) is left unspecified.

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% – from/to ISO 4217 codes and the amount default of 1 are all documented in the schema. The only extra meaning the description contributes is that valid codes are constrained to 150+ supported currencies, which is a marginal addition over the schema's format guidance. Baseline 3 is appropriate.

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 concrete verb and resource: convert an amount between two currencies. It also bounds scope (150+ currencies, daily rates). No sibling operates in this domain, so there is nothing to differentiate against, but the purpose is unambiguous.

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?

There is no guidance on when to use this versus anything else, no prerequisites, and no exclusions. Usage is only implied by the verb 'Convert', which is the minimum-viable case.

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