v1_fxCurrency exchange rates: Reference FX rates (ECB) with optional amount conversion. Source: Frankfurter (ECB) / open.er-api. $0.005 per call · GET /v1/fx
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | Target currency/currencies (comma-separated). Example: 'EUR,GBP,JPY'. | |
| from | Yes | Base currency ISO-4217. Example: 'USD'. | |
| amount | No | Amount to convert (default 1). Example: '100'. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds source (Frankfurter/ECB), pricing, and the GET endpoint, but does not disclose response shape, pagination, or potential error behavior.
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 a concise one-liner that front-loads the core purpose and includes useful metadata such as source, pricing, and HTTP method. It avoids filler, though the pricing detail is arguably non-essential.
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 3-parameter tool, the description plus schema covers what the tool does and how to invoke it. However, it omits the return format and does not differentiate when to use this tool versus unit conversion or crypto price tools, leaving some selection ambiguity.
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 the baseline is 3. The description's mention of 'optional amount conversion' loosely maps to the amount parameter but adds no syntax or edge-case detail beyond what the schema already provides.
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 identifies the resource as ECB reference FX rates and mentions optional amount conversion. This distinguishes it from generic unit conversion (v1_unit_convert) and crypto pricing (v1_crypto_price), though it lacks an explicit verb such as 'retrieve'.
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?
No guidance is given about when to use this tool versus alternatives like v1_unit_convert or v1_crypto_price. The description does not state scenarios, exclusions, or when a different tool would be more appropriate.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Every tool targets a distinct resource or operation—geocoding, weather, DNS, VIN, stock quotes, etc.—with no meaningful overlap in purpose. Even the location- and finance-related tools are clearly separated by their descriptions.
All tools follow the same v1_<resource>[_modifier] snake_case pattern, such as v1_air_quality, v1_reverse_geocode, and v1_validate_email. Although the names are not verb-based, the convention is perfectly consistent across all 31 tools.
31 tools exceeds the 25+ threshold and creates a heavy selection burden for agents, even though the server's stated purpose is broad. Many endpoints are small single-purpose lookups that could be grouped into fewer combined tools without losing clarity.
As a general public-data utility, the set covers a wide range of common lookup categories: location, weather, finance, legal, health, business, internet, and reference data. It has minor gaps like historical financial time series or phone-number validation, but no obvious dead ends since all tools are self-contained read-only lookups.