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

With no annotations, the description carries the full burden. It discloses the live data source (Frankfurter/ECB), what is returned (amount and rate), that the response omits timestamp/source attribution, and that crypto is unsupported. It also mentions fallback behavior when Frankfurter is rate-limited. However, it does not discuss error handling, invalid code behavior, or any potential side effects, so a small transparency gap remains.

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 longer than necessary but front-loaded: the first sentence states the core action, the second states the return value, and the rest is purposeful sibling differentiation. While the tool-selection guidance is verbose, it earns its place given the large sibling list. No filler words or tautology.

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?

The tool has no output schema, so the description must explain return values, and it does: 'Returns the converted amount and the exchange rate applied.' It also covers data source, response scope (minimal), and exclusions. Given that this is a simple conversion tool with three fully documented parameters, the description is contextually 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?

The input schema already covers parameter meaning 100%, so the baseline is 3. The description adds value by specifying 'fiat currencies' only, listing example ISO codes, and explicitly stating crypto pairs are not supported. This extra context helps disambiguate parameter constraints beyond the schema's generic 'ISO 4217 code' definitions.

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 ('Converts') and clear resource ('monetary amount between any two fiat currencies'), immediately distinguishing it from sibling tools. It further clarifies that this is a 'lightweight variant of currency_convert' with a minimal response, so the tool's 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?

The description provides explicit when-to-use guidance and names alternatives: use this when only converted value and rate are needed, prefer currency_convert when timestamp/richer output is needed, prefer currency_fx_lite when ECB source is not required, use currency_rates for historical, and currency_convert_open as a fallback. It also excludes crypto and directs to crypto_price/crypto_fx_rates, making selection among siblings very clear.

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