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SignalHarness EIP-191 Message Hash
x402
SignalHarness EIP-191 Message Hash is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-13).
Computes the EIP-191 Ethereum personal sign message hash for a given input string
Price / call$0.005
Success—
StatusUnknown
How this service works
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Output
Returns the EIP-191-prefixed keccak256 hash (message_hash) of the supplied input string, along with a list of any warnings about the input, the evidence_scope indicating data provenance, a replay-detection flag, and a full execution receipt including payment ID, network (Base), amount charged in atomic USDC units, and result SHA-256 for integrity verification.
Example use cases
Wallet signature verification prep
“I need the EIP-191 message hash for 'Login nonce: a3f9b2c1d4e5 for user alice@example.com' so I can verify an Ethereum wallet signature on my backend.”
Smart contract off-chain signing
“Can you hash this message using EIP-191 personal sign format: 'Approve transfer of 500 USDC to 0xDeadBeef00000000000000000000000000000000 on 2024-07-05'?”
Auth token hash for dApp login
“Hash the string 'dapp-session:user=0x1234567890abcdef&expires=1720100000' with EIP-191 so I know what digest MetaMask will actually sign.”
Technical details
Endpoint
POSThttps://signalharness.ai/api/agent/services/message_hash_eip191/invokeWhen to prefer
Choose this endpoint when you need a deterministic, auditable EIP-191 personal_sign message hash computed as a paid, receipted API call with on-chain payment provenance on Base — useful when you need cryptographic evidence of what was hashed and by whom, rather than computing locally. Prefer local computation for high-volume or latency-sensitive use cases; use this when auditability, receipts, or agent-native x402 payment rails are required.
Side effects
- Input string too short (below minLength of 2) — validation error returned
- Input string exceeds 65536 characters — request rejected
- Malformed JSON body — HTTP 400
- Payment failure or insufficient USDC balance — HTTP 402 with payment details
- Service unavailable — HTTP 5xx with error message
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| message_hash_request | string |
Output
Schema · Response
{
"type": "json",
"example": {
"replay": false,
"result": {
"warnings": [
"Hashing does not sign or prove authorship."
],
"service_id": "message_hash_eip191",
"message_hash": "{\"encoding\":\"utf8\",\"hash\":\"0x43c3ce76740c0da4b23274e62f830220acfc4cb8d66dc3c373c6f58db8620442\"}",
"evidence_scope": "caller_supplied_data"
},
"status": "succeeded",
"receipt": {
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"usage": [],
"status": "succeeded",
"network": "eip155:8453",
"artifacts": [],
"endedAtMs": 0,
"latencyMs": 0,
"paymentId": "example-payment",
"receiptId": "example-receipt",
"requestId": "example-request",
"serviceId": "message_hash_eip191",
"executionId": "example-execution",
"startedAtMs": 0,
"amountAtomic": "5000",
"resultSha256": "8f11719349cff4ac11654fa2d877a1171776a9cc3eee1fc4857fac9b56d1829f",
"serviceVersion": "1.0.0",
"settlementReference": "0x0000000000000000000000000000000000000000000000000000000000000000"
},
"artifacts": [],
"requestId": "example-request",
"executionId": "example-execution"
}
}Tags
x402
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