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

Annotations already cover the read-only, open-world safety profile, so the description only needs to add context — and it does: the ECB reference source, the 30+ currency scope, and crucially the $0.0035 USDC x402 cost per call. Return format and rate freshness/latency are not disclosed.

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 capability, then parameters, then cost. Nothing is padded; the only weak spot is that the pricing sentence could be integrated more tightly.

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?

With no output schema, the description should say more about what a call returns (rate table vs converted amount, rounding, timestamp). It covers sources and cost well but leaves the response shape entirely to inference for a tool that has two distinct output modes.

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 67%, and the description only restates 'base, symbols and an optional amount' without adding syntax or constraints. The one useful addition is flagging that amount is optional (i.e. only needed for conversion), which the schema leaves blank, but this is modest compensation for the coverage gap.

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+resource: live FX rates and conversion, with the data source (ECB reference) and currency count. 'Live' implicitly separates it from the fx_history sibling, though it never names that sibling or the generic 'convert' tool it partially overlaps with.

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 only implied: 'Live' suggests current rates rather than history, and the optional amount hints that supplying it switches to conversion. There is no explicit when-to-use statement, no exclusions, and no pointer to fx_history or convert for adjacent needs.

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