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Blackwood State

by io.github.Blackwood-State
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Currency exchange rates

blackwood_fx_rates
Read-onlyIdempotent

Use when you need currency exchange rates, fx rates or forex conversion of an amount between two currencies like EUR and GBP. Do not use for live trading quotes, intraday or crypto rates (ECB rates update once per business day). Returns JSON with currency exchange rates: official ECB euro reference FX rates (free at ecb.europa.eu) for about 30 currencies, rebased to any base as cross rates, with optional conversion for 0.005 USDC per call. Typical response time 1500 ms (p95). Category: Data.

Input Schema

NameRequiredDescriptionDefault
baseNoBase currency, ISO 4217 (EUR when omitted), e.g. USD
amountNoAmount in the base currency to convert, e.g. 100
symbolsNoCurrencies to return, e.g. ["BRL", "JPY"] (all ECB currencies when omitted)
response_formatNoconcise (the default when omitted) keeps the JSON short: long fields such as base64 images or audio come back as separate image/audio content blocks and other long strings are cut with a marker; detailed returns the full JSON

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / anyOf
      Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "amount": {
-        "type": [
-          "number",
-          "null"
-        ]
-      },
-      "attribution": {
-        "type": "string"
-      },
-      "base": {
-        "type": "string"
-      },
-      "converted": {
-        "anyOf": [
-          {
-            "additionalProperties": {
-              "type": "number"
-            },
-            "propertyNames": {
-              "type": "string"
-            },
-            "type": "object"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "date": {
-        "type": "string"
-      },
-      "note": {
-        "type": "string"
-      },
-      "rates": {
-        "additionalProperties": {
-          "type": "number"
-        },
-        "propertyNames": {
-          "type": "string"
-        },
-        "type": "object"
-      }
-    },
-    "required": [
-      "date",
-      "base",
-      "rates",
-      "amount",
-      "converted",
-      "attribution",
-      "note"
-    ],
-    "type": "object"
-  },
-  {
-    "description": "x402 PaymentRequired (returned with isError when payment is needed)",
-    "properties": {
-      "accepts": {
-        "items": {
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "error": {
-        "type": "string"
-      },
-      "extensions": {
-        "type": "object"
-      },
-      "resource": {
-        "type": "object"
-      },
-      "x402Version": {
-        "type": "integer"
-      }
-    },
-    "required": [
-      "x402Version",
-      "accepts"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "amount": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "attribution": {
+        "type": "string"
+      },
+      "base": {
+        "type": "string"
+      },
+      "converted": {
+        "anyOf": [
+          {
+            "additionalProperties": {
+              "type": "number"
+            },
+            "propertyNames": {
+              "type": "string"
+            },
+            "type": "object"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "date": {
+        "type": "string"
+      },
+      "next": {
+        "additionalProperties": false,
+        "description": "Suggested next paid call in the same family (call it in a loop when the task continues)",
+        "properties": {
+          "method": {
+            "enum": [
+              "GET",
+              "POST"
+            ],
+            "type": "string"
+          },
+          "sample": {
+            "description": "Free fixed sample of the whole family",
+            "type": "string"
+          },
+          "service": {
+            "description": "Service id of the suggested next paid call",
+            "type": "string"
+          },
+          "tool": {
+            "description": "MCP tool name of the same call",
+            "type": "string"
+          },
+          "url": {
+            "description": "Paid route of the next call",
+            "type": "string"
+          },
+          "useWhen": {
+            "description": "When the next call is the right one",
+            "type": "string"
+          }
+        },
+        "required": [
+          "service",
+          "tool",
+          "method",
+          "url",
+          "useWhen",
+          "sample"
+        ],
+        "type": "object"
+      },
+      "note": {
+        "type": "string"
+      },
+      "rates": {
+        "additionalProperties": {
+          "type": "number"
+        },
+        "propertyNames": {
+          "type": "string"
+        },
+        "type": "object"
+      }
+    },
+    "required": [
+      "date",
+      "base",
+      "rates",
+      "amount",
+      "converted",
+      "attribution",
+      "note"
+    ],
+    "type": "object"
+  },
+  {
+    "description": "x402 PaymentRequired (returned with isError when payment is needed)",
+    "properties": {
+      "accepts": {
+        "items": {
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "error": {
+        "type": "string"
+      },
+      "extensions": {
+        "type": "object"
+      },
+      "resource": {
+        "type": "object"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "required": [
+      "x402Version",
+      "accepts"
+    ],
+    "type": "object"
+  }
+]
  2. Added

TDQS

A4.1/5.0
Behavior5/5

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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description goes well beyond them: cost (0.005 USDC per call), latency (1500 ms p95), data freshness (once per business day), source and licensing (ECB, free), and currency coverage (~30). This is exactly the operational context an agent needs before invoking.

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?

Front-loaded with the 'Use when' trigger, then exclusions, then return/cost/latency facts in a compact run. Minor waste in the near-synonym list 'currency exchange rates, fx rates or forex conversion' and the trailing 'Category: Data' label, but the structure is otherwise tight.

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?

An output schema exists, so return formatting need not be explained, yet the description still covers data source, coverage, cost, latency and refresh cadence. Combined with the full schema coverage and rich annotations, nothing essential is missing for correct invocation.

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

Parameters3/5

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

Schema description coverage is 100%, so all four parameters are already documented with types, patterns and defaults. The description adds only marginal semantics ('rebased to any base as cross rates', 'optional conversion'), which is the expected baseline when the schema does the heavy lifting.

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

Purpose4/5

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

States a specific verb and resource ('currency exchange rates', 'fx rates', 'forex conversion of an amount') and pins down the data source (official ECB euro reference rates, ~30 currencies, rebased as cross rates). It clearly distinguishes itself from live/intraday and crypto rate tools, but never differentiates from the sibling blackwood_fx_history, which an agent could plausibly confuse with this tool.

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 an explicit 'Use when' trigger and an explicit 'Do not use for' exclusion (live trading quotes, intraday, crypto), with the reason (ECB updates once per business day). It stops short of naming the correct alternative tool for historical or crypto rates, so the routing guidance is strong but not complete.

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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