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

With no annotations, the description carries the full burden and it does well by disclosing the data source (Frankfurter/ECB), return contents (converted amount and exchange rate), and the minimal response nature (no rate timestamp or source attribution). It also notes the lack of crypto support. It stops short of discussing error behavior or rate limits, but the key behavioral traits are covered.

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 front-loaded with purpose and output, followed by sibling comparisons and exclusions. While longer than average, each sentence contributes meaningful selection guidance. It could be condensed slightly, but the structure is logical and efficient.

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 conversion tool with no output schema and no annotations, the description provides sufficient context for an agent to select and invoke it correctly. It specifies return values, alternative tools, non-supported use cases (crypto), and gives currency code examples, making the tool's behavior and boundaries clear.

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%, with each parameter (amount, from, to) already described with format and constraints. The description adds only marginal context, such as 'any two fiat currencies' and example ISO codes, but does not materially enhance parameter understanding beyond the schema.

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 opens with a specific verb and resource: 'Converts a monetary amount between any two fiat currencies using live exchange rates from the Frankfurter API (European Central Bank data).' It clearly distinguishes itself from sibling tools by identifying as a 'lightweight variant of currency_convert' and contrasting with currency_convert, currency_fx_lite, currency_rates, and currency_convert_open.

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 guidance is explicit and actionable: 'Use currency_convert_lite when only the converted value and rate are needed,' with specific instructions to prefer currency_convert for richer output, currency_fx_lite when ECB sourcing isn't required, currency_rates for historical data, and currency_convert_open as a fallback. It also excludes crypto pairs, directing users to crypto_price or crypto_fx_rates.

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