Latest FX rates (ECB / Frankfurter)

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true. The description adds the source (European Central Bank) and clarifies that rates are returned for specified symbols against a base currency. This is consistent but adds minimal new behavioral context beyond the annotations.

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 two concise sentences that front-load the source and purpose. Every word adds value; there is no unnecessary information. It is perfectly sized for a simple read-only tool.

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 read-only tool with no output schema, the description explains what it returns and the role of parameters. However, it lacks differentiation from sibling tools (e.g., fx_open_rates, fx_historical_rate) and does not mention update frequency or error handling. It is adequate but not comprehensive.

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 description coverage is 100% for both parameters: 'base' and 'symbols' have clear descriptions. The tool description adds the relationship 'Returns rates for `symbols` quoted against `base`', which is helpful but not essential given the schema already explains each parameter. 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 clearly specifies the verb 'Returns' and resource 'latest foreign-exchange reference rates' from the European Central Bank. It also mentions the parameters `symbols` and `base`. However, it does not explicitly differentiate from sibling tools like fx_historical_rate or fx_open_rates, which also provide exchange rate data.

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 tool versus alternatives such as fx_open_rates or fx_historical_rate. The description only explains the parameters but does not state the typical use case or circumstances where this tool is preferred.

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