exchange_rates

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

With no annotations at all, the description carries the full burden and does well: it names the authoritative source (ECB), publication cadence (every working day ~16:00 CET), return shape, cost ($0.0045 USDC per call) and p99 latency (300ms). Those are exactly the traits an agent needs to decide whether to call it.

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?

Densely front-loaded with the identity and source first, then usage, then cost/latency — a sensible ordering. Minor redundancy in the opening ('Currency Exchange Rates — Currency exchange rates (forex)') that repeats the title.

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?

There is no output schema, but the description compensates by describing the return as a rates object keyed by currency code relative to base. Cost, latency, cadence, and coverage are all present; only error/edge-case behavior (e.g. unsupported symbol) is unaddressed.

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 the schema, including the 'empty = all' semantics. The description restates the symbols filtering and the concept of a base currency but adds no format, validation, or unsupported-currency behavior 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?

States a specific resource (official ECB forex reference rates), scope (~30 currencies including USD/GBP/CHF/JPY/CNY) and capability (cross rates for any base). It does not explicitly distinguish itself from the nearby crypto_prices sibling, which the agent could plausibly confuse for currency conversion.

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?

"Use for currency conversion in invoices, pricing, or financial calculations" gives concrete usage context, and it explains the symbols filter (empty = all supported). It lacks any when-not guidance or alternative routing, but the domain is narrow enough that this is a minor gap.

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