Frankfurter exchange rates: latest

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

Annotations only declare readOnly and openWorld, so the description usefully adds that rates are ECB reference rates updated once per working day - important context that the data may be stale within a day. It also discloses the return shape (base, date, rates map). Missing only exotics like rate limits or error behavior, which matters less for an open public API.

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 domain tag and the core action; the omission rule and return example are each one clause. Nothing waste-like or redundant with the schema.

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?

No output schema exists, but the description compensates by sketching the response object (base, date, rates, rates.CNY). For a two-optional-parameter read tool this is nearly complete; only auth/error behavior is unstated.

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%, so both parameters are already documented in structured form. The description only adds the default-full-set behavior for omitting symbols and the ~30 currency count, which is a modest increment over the schema rather than new semantics for base.

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?

Names a specific verb and resource ("Get the latest European Central Bank reference exchange rates") plus the source and update cadence. No sibling tool overlaps with currency rates, so no differentiation is needed, and the tag prefix makes its domain obvious at a glance.

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?

Gives concrete operational guidance: base currency selects the pivot, and "Omit symbols to get all ~30 currencies" tells the agent exactly how to get the full set. It stops short of when-not-to-use or alternative-source guidance, but the sibling list contains no competing tool.

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