Agent Decision & Evidence Tools (MCP + x402)

Multi-source crypto spot median

spot_price

Read-only

Attempt independent Binance, Coinbase and Kraken public tickers and calculate the median from the live quotes that return. Every delivered quote, quote currency, spread and timestamp is disclosed; fewer than two live sources is an uncharged error.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`symbol`	No		BTC

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No
`tool`	No
`as_of`	No
`error`	No
`method`	No
`symbol`	No
`charged`	No	When present on an error, false means the failed result is uncharged.
`message`	No
`missing`	No
`receipt`	No
`settled`	No	When present on an error, false means no settlement occurred.
`sources`	No
`unknown`	No
`accepted`	No
`price_usd`	No
`retryable`	No
`error_code`	No
`extensions`	No
`spread_pct`	No
`status_code`	No
`did_you_mean`	No
`missing_checks`	No
`sources_failed`	No
`partial_evidence`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 6, 2026

addedInput schema / additionalProperties
```
Added value: +false
```
removedInput schema / properties / symbol / title
```
Removed value: -"Symbol"
```

removedInput schema / title

Removed value: -"spot_price_toolArguments"

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "anyOf": [
+    {
+      "required": [
+        "symbol",
+        "price_usd",
+        "method",
+        "sources",
+        "sources_failed",
+        "spread_pct",
+        "as_of",
+        "note",
+        "receipt",
+        "extensions"
+      ]
+    },
+    {
+      "required": [
+        "error"
+      ]
+    }
+  ],
+  "description": "Structured result contract for spot_price. A success satisfies the documented success branch. A domain or tool error includes error and is not a successful settlement; unpaid x402 requirements are carried by the transport wrapper.",
+  "properties": {
+    "accepted": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "as_of": {
+      "type": "string"
+    },
+    "charged": {
+      "description": "When present on an error, false means the failed result is uncharged.",
+      "type": "boolean"
+    },
+    "did_you_mean": {
+      "additionalProperties": true,
+      "type": [
+        "object",
+        "null"
+      ]
+    },
+    "error": {
+      "oneOf": [
+        {
+          "type": "string"
+        },
+        {
+          "additionalProperties": true,
+          "properties": {
+            "code": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "message": {
+              "type": "string"
+            },
+            "param": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "type": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "message"
+          ],
+          "type": "object"
+        }
+      ]
+    },
+    "error_code": {
+      "type": "string"
+    },
+    "extensions": {
+      "additionalProperties": true,
+      "properties": {
+        "delivery-receipt": {
+          "additionalProperties": true,
+          "properties": {
+            "how_to_verify": {
+              "type": "string"
+            },
+            "issued_at": {
+              "format": "date-time",
+              "type": "string"
+            },
+            "issuer": {
+              "type": "string"
+            },
+            "issuer_key": {
+              "type": "string"
+            },
+            "key_id": {
+              "type": "string"
+            },
+            "result_hash": {
+              "type": "string"
+            },
+            "service": {
+              "type": "string"
+            },
+            "signature": {
+              "type": "string"
+            },
+            "signed_message": {
+              "type": "string"
+            },
+            "standard": {
+              "const": "eucompliance-receipt/2",
+              "type": "string"
+            },
+            "subject": {
+              "type": "string"
+            },
+            "valid_until": {
+              "format": "date-time",
+              "type": "string"
+            },
+            "verify_url": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "standard",
+            "service",
+            "subject",
+            "result_hash",
+            "issued_at",
+            "valid_until",
+            "issuer",
+            "issuer_key",
+            "key_id",
+            "verify_url",
+            "how_to_verify",
+            "signature",
+            "signed_message"
+          ],
+          "type": "object"
+        }
+      },
+      "required": [
+        "delivery-receipt"
+      ],
+      "type": "object"
+    },
+    "message": {
+      "type": "string"
+    },
+    "method": {
+      "type": "string"
+    },
+    "missing": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "missing_checks": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "note": {
+      "type": "string"
+    },
+    "partial_evidence": {
+      "additionalProperties": true,
+      "type": "object"
+    },
+    "price_usd": {
+      "type": "number"
+    },
+    "receipt": {
+      "additionalProperties": true,
+      "properties": {
+        "how_to_verify": {
+          "type": "string"
+        },
+        "issued_at": {
+          "format": "date-time",
+          "type": "string"
+        },
+        "issuer": {
+          "type": "string"
+        },
+        "issuer_key": {
+          "type": "string"
+        },
+        "key_id": {
+          "type": "string"
+        },
+        "result_hash": {
+          "type": "string"
+        },
+        "service": {
+          "type": "string"
+        },
+        "signature": {
+          "type": "string"
+        },
+        "signed_message": {
+          "type": "string"
+        },
+        "standard": {
+          "const": "eucompliance-receipt/2",
+          "type": "string"
+        },
+        "subject": {
+          "type": "string"
+        },
+        "valid_until": {
+          "format": "date-time",
+          "type": "string"
+        },
+        "verify_url": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "standard",
+        "service",
+        "subject",
+        "result_hash",
+        "issued_at",
+        "valid_until",
+        "issuer",
+        "issuer_key",
+        "key_id",
+        "verify_url",
+        "how_to_verify",
+        "signature",
+        "signed_message"
+      ],
+      "type": "object"
+    },
+    "retryable": {
+      "type": "boolean"
+    },
+    "settled": {
+      "description": "When present on an error, false means no settlement occurred.",
+      "type": "boolean"
+    },
+    "sources": {
+      "items": {},
+      "type": "array"
+    },
+    "sources_failed": {
+      "items": {},
+      "type": "array"
+    },
+    "spread_pct": {
+      "type": "number"
+    },
+    "status_code": {
+      "type": "integer"
+    },
+    "symbol": {
+      "type": "string"
+    },
+    "tool": {
+      "type": "string"
+    },
+    "unknown": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

AddedSep 6, 2026

TDQS

A4.1/5.0

Behavior5/5

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

Beyond the readOnly/not-destructive annotations, the description discloses meaningful behaviors: independent source attempts, median calculation from only returning live quotes, full disclosure of quotes/currency/spread/timestamp, and the specific failure mode where fewer than two live sources produces an uncharged error.

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

Conciseness5/5

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

The description is two dense sentences with no filler. The first sentence front-loads the fetching and median mechanism; the second explains output disclosure and error behavior. Every clause earns its place.

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

Completeness4/5

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

With an output schema present and annotations covering safety, the description sufficiently explains sources, median calculation, disclosure, and failure semantics. It is only missing explicit symbol-format guidance or an example, leaving minor ambiguity for non-default symbols.

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

Parameters2/5

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

Schema description coverage is 0%, and the description never explains the symbol parameter or its accepted format, such as whether to use BTC vs BTCUSDT. The default value and parameter name give some inference, but the description does not compensate for the schema's lack of documentation.

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?

The description names a specific operation: attempting public tickers from Binance, Coinbase and Kraken and calculating the median of live quotes. It clearly identifies the resource as multi-source crypto spot pricing and distinguishes it from siblings like perp_market_data and market_history.

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

Usage Guidelines3/5

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

Usage context is implied: this tool is for spot median crypto prices across three named exchanges. However, the description does not explicitly state when to prefer it over alternatives such as market_data or perp_market_data, nor does it give when-not-to-use guidance.

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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