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SignCheck: Check before signing

check_signature

Read-onlyIdempotent

Call BEFORE your agent signs or sends anything from a wallet. Decodes a transaction, EIP-712 typed data (Permit, Permit2, EIP-3009 USDC authorizations, Seaport orders), an EIP-7702 delegation or an x402 payment (402 terms + payload) into plain English and returns SAFE / CAUTION / DANGER with risk flags (unlimited approvals, setApprovalForAll, fake USDC domains, x402 overpay or wrong payTo, OFAC SDN counterparties). Free preview tier (offline); paid check adds on-chain facts and an eth_call simulation. Not for: token due diligence (use check_token) or address screening alone (use screen_address).

[SignCheck via YourAITools MCP Hub] Free tier: same as SignCheck's own MCP server (call without payment and without tier). Paid: lite $0.005 / check $0.015 per call, with a credits key (Authorization: Bearer yatc_...) or x402 (USDC; the hub returns the payment terms). Failed tool calls aren't charged: credits are refunded automatically and x402 payments only settle on success.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "check_signature"
  }
}

Input Schema

Name	Required	Description
`tx`	No	Transaction to send: {"to":"0x…","data":"0x…","value":"0","from":"0x…"} (from enables simulation)
`tier`	No	Paid tier: lite $0.005, check $0.015. Omit tier (with no credits key or x402 payment) to use the free tier.
`chain`	No	base (default), ethereum, base-sepolia or a chain id
`typed_data`	No	EIP-712 request {domain, types, primaryType, message} as passed to eth_signTypedData_v4
`authorization`	No	EIP-7702 authorization {address (delegate contract), chainId, nonce}
`payment_payload`	No	x402 payment you are about to send: PAYMENT-SIGNATURE / X-PAYMENT (base64) or JSON
`payment_required`	No	x402 402 terms: the PAYMENT-REQUIRED header (base64) or JSON {accepts:[…]}

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 30, 2026

addedInput schema / properties / chain / examples
```
Added value: +[
+  "base"
+]
```

addedInput schema / properties / tx / examples

Added value: +[
+  {
+    "data": "0x095ea7b30000000000000000000000001111111254eeb25477b68fb85ed929f73a960582ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+    "to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
+    "value": "0"
+  }
+]

Changed8 schema fields changedOct 24, 2026

removedInput schema / properties / authorization / additionalProperties
```
Removed value: -true
```

changedInput schema / properties / payment_payload / anyOf

Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "additionalProperties": true,
-    "description": "The x402 payment payload the agent is about to send.",
-    "properties": {
-      "network": {
-        "type": "string"
-      },
-      "payload": {
-        "additionalProperties": true,
-        "properties": {
-          "signature": {
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "scheme": {
-        "type": "string"
-      },
-      "x402Version": {
-        "type": "integer"
-      }
-    },
-    "type": "object"
-  }
-]New value: +[
+  {
+    "type": "string"
+  },
+  {
+    "description": "The x402 payment payload the agent is about to send.",
+    "properties": {
+      "network": {
+        "type": "string"
+      },
+      "payload": {
+        "properties": {
+          "signature": {
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "scheme": {
+        "type": "string"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "type": "object"
+  }
+]

changedInput schema / properties / payment_required / anyOf

Previous value: -[
-  {
-    "type": "string"
-  },
-  {
-    "additionalProperties": true,
-    "description": "The x402 402 response body or decoded PAYMENT-REQUIRED header.",
-    "properties": {
-      "accepts": {
-        "items": {
-          "additionalProperties": true,
-          "properties": {
-            "network": {
-              "type": "string"
-            },
-            "payTo": {
-              "type": "string"
-            },
-            "scheme": {
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "x402Version": {
-        "type": "integer"
-      }
-    },
-    "type": "object"
-  }
-]New value: +[
+  {
+    "type": "string"
+  },
+  {
+    "description": "The x402 402 response body or decoded PAYMENT-REQUIRED header.",
+    "properties": {
+      "accepts": {
+        "items": {
+          "properties": {
+            "network": {
+              "type": "string"
+            },
+            "payTo": {
+              "type": "string"
+            },
+            "scheme": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "type": "object"
+  }
+]

removedInput schema / properties / tx / additionalProperties
```
Removed value: -true
```
removedInput schema / properties / typed_data / additionalProperties
```
Removed value: -true
```
removedInput schema / properties / typed_data / properties / domain / additionalProperties
```
Removed value: -true
```
removedInput schema / properties / typed_data / properties / message / additionalProperties
```
Removed value: -true
```
removedInput schema / properties / typed_data / properties / types / additionalProperties
```
Removed value: -true
```

Changed10 schema fields changedOct 24, 2026

addedInput schema / properties / authorization / additionalProperties
```
Added value: +true
```

addedInput schema / properties / authorization / properties

Added value: +{
+  "address": {
+    "type": "string"
+  },
+  "chainId": {
+    "type": "integer"
+  },
+  "nonce": {
+    "type": "integer"
+  }
+}

addedInput schema / properties / payment_payload / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "additionalProperties": true,
+    "description": "The x402 payment payload the agent is about to send.",
+    "properties": {
+      "network": {
+        "type": "string"
+      },
+      "payload": {
+        "additionalProperties": true,
+        "properties": {
+          "signature": {
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "scheme": {
+        "type": "string"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "type": "object"
+  }
+]

removedInput schema / properties / payment_payload / type
```
Removed value: -[
-  "object",
-  "string"
-]
```

addedInput schema / properties / payment_required / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "additionalProperties": true,
+    "description": "The x402 402 response body or decoded PAYMENT-REQUIRED header.",
+    "properties": {
+      "accepts": {
+        "items": {
+          "additionalProperties": true,
+          "properties": {
+            "network": {
+              "type": "string"
+            },
+            "payTo": {
+              "type": "string"
+            },
+            "scheme": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "type": "object"
+  }
+]

removedInput schema / properties / payment_required / type
```
Removed value: -[
-  "object",
-  "string"
-]
```
addedInput schema / properties / tx / additionalProperties
```
Added value: +true
```

addedInput schema / properties / tx / properties

Added value: +{
+  "chainId": {
+    "type": "integer"
+  },
+  "data": {
+    "type": "string"
+  },
+  "from": {
+    "type": "string"
+  },
+  "to": {
+    "type": "string"
+  },
+  "value": {
+    "type": "string"
+  }
+}

addedInput schema / properties / typed_data / additionalProperties
```
Added value: +true
```

addedInput schema / properties / typed_data / properties

Added value: +{
+  "domain": {
+    "additionalProperties": true,
+    "properties": {
+      "chainId": {
+        "type": "integer"
+      },
+      "name": {
+        "type": "string"
+      },
+      "verifyingContract": {
+        "type": "string"
+      },
+      "version": {
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "message": {
+    "additionalProperties": true,
+    "properties": {
+      "owner": {
+        "type": "string"
+      },
+      "spender": {
+        "type": "string"
+      },
+      "value": {
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "primaryType": {
+    "type": "string"
+  },
+  "types": {
+    "additionalProperties": true,
+    "properties": {
+      "EIP712Domain": {
+        "items": {
+          "properties": {
+            "name": {
+              "type": "string"
+            },
+            "type": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "type": "object"
+  }
+}

First observedOct 24, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: the tiered output vocabulary, the distinction between the offline free preview and the simulation-backed paid tier, the auth mechanisms (Bearer yatc_ key or x402 USDC), pricing, and the no-charge-on-failure refund behavior. None of this contradicts the readOnly/non-destructive annotations.

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 imperative call-timing, then capability, then exclusions — good ordering. The trailing hub/pricing paragraph is longer than strictly necessary for tool selection and repeats some of the tier info already given, which keeps it from a 5.

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 seven optional parameters and no output schema or required fields, an agent needs to know which input shape to supply and what comes back; the description covers both by enumerating input artifact types and naming the verdict vocabulary and risk flags. Cost, auth, and refund behavior fill the remaining gaps for an open-world paid tool.

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 goes further by mapping real-world scenarios onto parameters: Permit/Permit2/EIP-3009/Seaport map to typed_data, EIP-7702 delegation maps to authorization, and the 402 terms + payload mapping to payment_required/payment_payload. That disambiguation of seven mutually optional params is genuinely beyond the schema text.

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 (decodes) and enumerates exactly which artifacts it handles: transactions, EIP-712 typed data with named subtypes, EIP-7702 delegations, and x402 payments. It also states the output form (SAFE / CAUTION / DANGER with named risk flags) and explicitly disclaims token due diligence and address screening in favor of check_token and screen_address, so it is unmistakable against siblings.

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

Usage Guidelines5/5

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

Gives an explicit call-site instruction ('Call BEFORE your agent signs or sends anything from a wallet') plus an explicit 'Not for:' list naming the two sibling alternatives for adjacent jobs. The free-vs-paid tradeoff is also spelled out (free = offline preview, paid = on-chain facts + eth_call simulation), which tells the agent when the cheap path is insufficient.

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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