LogicNodes

Currency conversion at official ECB reference rates (dated, never guessed)

fx_rate

Read-only

[FREE: 25 calls/day, then $0.002 USDC per call via x402] Converts between about 30 currencies (USD, EUR, GBP, JPY, CAD, AUD, CHF, CNY, INR, MXN, BRL, ...) at the European Central Bank's euro reference rates, published once per business day around 16:00 CET. Cross rates go through the euro exactly as the ECB publishes them. Give a date (last 90 days) or get the latest; a weekend or holiday uses the last published rates and says which. Returns each rate, its inverse, the converted amount (rounded to the currency scale you choose) and the rate date. Reference rates are for information: banks and card networks add their own margins.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "from": "<from>",
      "to": "<to>"
    },
    "name": "fx_rate"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	one or more target codes, e.g. ["EUR", "GBP"]
`date`	No	rates for this date (within the last 90 days); default the latest
`from`	Yes	ISO 4217 code, e.g. USD
`scale`	No	decimal places of converted amounts, default 2
`amount`	No	amount to convert as a decimal string, default "1"
`rounding`	No	default half_up

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 30, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the readOnly/openWorld annotations: pricing tier (25 free calls/day, then $0.002 USDC via x402), ECB publication cadence (~16:00 CET business days), cross-rate mechanics via the euro, and explicit holiday fallback behavior with a stated rate date. This is exactly the operational context an agent needs before calling.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

One dense but well-ordered paragraph: pricing, coverage, source, mechanics, date rules, return shape, caveat. Front-loading the cost bracket is arguably a distraction from the core purpose, and it is longer than strictly necessary, but no sentence is filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 6 parameters and no output schema, the description still explains what comes back (each rate, its inverse, converted amount, rate date) and covers the edge cases an agent would otherwise have to discover by trial. Nothing material is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: the 90-day date window, the 'latest' default, currency-scale rounding, and the fact that each result includes inverse rates and the rate date. It doesn't explain the rounding enum values or the 30-target cap, which the schema already handles.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (converts between ~30 currencies) and pins the data source (ECB euro reference rates), which distinguishes it from generic siblings like money_calc, unit_convert, or token_price.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete calling contexts: supply a date within 90 days or omit it for the latest, and weekends/holidays silently fall back to the last published rates. It also warns that these are informational reference rates, not bank/card rates. It doesn't name a specific sibling alternative, so it stops short of a 5.

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

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