get_fx_rate_currentReturns the current exchange rate for a G10 currency pair. Source: European Central Bank. Supported: EURUSD, GBPUSD, USDJPY, USDCHF, USDCAD, AUDUSD, NZDUSD, USDSEK, USDNOK. Price: $0.01 USDC per call via x402 (Base or Solana).
| Name | Required | Description | Default |
|---|---|---|---|
| pair | Yes | G10 currency pair, e.g. EURUSD |
Changes observed during successful MCP inspections.
Input schema / properties / pair / descriptionPrevious value: -"G10 currency pair e.g. EURUSD, USDJPY, GBPUSD"New value: +"G10 currency pair, e.g. EURUSD"Output schema / (root)Previous value: -{
- "$schema": "http://json-schema.org/draft-07/schema#",
- "additionalProperties": false,
- "properties": {
- "date": {
- "description": "Date of the rate (YYYY-MM-DD)",
- "type": "string"
- },
- "label": {
- "description": "Human-readable pair name",
- "type": "string"
- },
- "pair": {
- "description": "Currency pair identifier",
- "type": "string"
- },
- "rate": {
- "description": "Current exchange rate",
- "type": "string"
- }
- },
- "required": [
- "pair",
- "label",
- "rate",
- "date"
- ],
- "type": "object"
-}New value: +nullDoes the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover safety (readOnly, idempotent, non-destructive), and the description adds genuinely new context: the ECB data source and, importantly, a $0.01 USDC per-call cost via x402 on Base or Solana. It stops short of stating data refresh cadence or staleness, which would matter for a 'current' rate.
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 tight sentences, front-loaded with purpose and then source and price. The enumerated pair list slightly duplicates the schema enum, a minor redundancy.
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 tells the agent it receives an exchange rate, plus source and cost, which is enough to call correctly. Return format and update frequency are the only omissions.
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 description coverage is 100% and the pair argument is a fully enumerated type, so the schema already carries the burden. The description's list of supported pairs merely restates the enum rather than adding format or semantics.
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 names a specific verb and resource ('Returns the current exchange rate for a G10 currency pair') and the word 'current' implicitly separates it from historical siblings like get_fx_rate_by_date and get_fx_rate_series.
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?
The scope is implied by 'current' exchange rate, but the description never states when to pick this over get_fx_rate_by_date or get_fx_rate_series, and gives no exclusions or preconditions.
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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