frankfurter_latest

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

Annotations already mark readOnlyHint=true, so description's job is lighter. The description adds valuable behavioral context: update frequency ('once per business day at ~16:00 CET'), data source (ECB), and the nature of rates ('reference rates, not real-time'). These go beyond the annotations and help set expectations.

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 sentences, each essential: function+source, output scope, update schedule+caveat. No wasted words. Front-loaded with the core action.

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?

Given no output schema, the description could briefly mention the return format (e.g., JSON with base, date, and rates). It does not cover error states or weekend behavior. However, it is adequate for a simple tool with clear parameters and good annotations.

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 descriptions for both parameters. The tool description adds no additional parameter information beyond what the schema already provides (e.g., 'base' default and length, 'symbols' format). Baseline score of 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?

Description explicitly states 'Get latest forex exchange rates from the European Central Bank', which is a specific verb+resource. It distinguishes from sibling tools like frankfurter_historical and frankfurter_timeseries by focusing on the latest rates. The caveat about reference rates vs real-time further clarifies scope.

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?

Description implies usage context: for the most recent daily reference rates, not real-time trading rates. It does not explicitly list alternatives or when-not-to-use, but the sibling set and the description's clarity provide good guidance for an agent.

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