# touchstone.locomot.io – EIP-191 Signature Verification (ecrecover)

> touchstone.locomot.io – EIP-191 Signature Verification (ecrecover) is a paid API for AI agents from touchstone.locomot.io, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Recovers the Ethereum address that signed a message using ecrecover / EIP-191 personal_sign, optionally validating against an expected signer address.

## Facts

- Endpoint: GET https://touchstone.locomot.io/verify/sig
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/touchstone-locomot-io-eip-191-signature-verification-ecrecover-a97e7ba9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_mAMM5H2QiF0Sd7ASDk4LM

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability touchstone-locomot-io-eip-191-signature-verification-ecrecover-a97e7ba9
```

Example prompt: Can you recover which Ethereum wallet signed this message — 'Hello World' — given the signature 0x4a5f...d3e2? Also check if it matches the expected signer 0xAbCd...1234.

## When to prefer this

Use this endpoint when you need to recover the signing Ethereum address from a standard EIP-191 personal_sign signature (the most common Web3 message signing format). If you are working with EIP-712 typed structured data, use the POST /verify/sig endpoint instead. Prefer this over rolling your own ecrecover logic when you want a deterministic, signed, auditable answer from a neutral third-party service.

## Known failure modes

- Invalid or malformed signature hex returns an error (cannot ecrecover)
- Message format mismatch causes incorrect signer recovery
- Missing required 'signature' or 'message' query parameters returns a 400-level error
- Expected_signer address format is invalid (non-checksummed or malformed)
- Signature produced by a different scheme (e.g. EIP-712) will yield incorrect or unexpected signer — use POST /verify/sig for typed data

## How this service works

Recover who signed a message (ecrecover, EIP-191 personal_sign). For EIP-712 typed data use POST /verify/sig. Every answer signed.

## Output

Returns a JSON object containing the recovered signer Ethereum address, the message digest, the signature scheme (e.g. eip191), a boolean 'matches' field indicating whether the recovered signer equals the expected_signer (if provided), and the source/op metadata. The response itself is signed by the Touchstone service.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "signature",
      "message"
     ],
     "properties": {
      "type": {
       "type": "string",
       "description": "eip191"
      },
      "message": {
       "type": "string",
       "description": "signed message (text or 0x-hex)"
      },
      "signature": {
       "type": "string",
       "description": "0x-hex signature"
      },
      "expected_signer": {
       "type": "string",
       "description": "optional address to match against"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "properties": {
    "op": {
     "type": "string"
    },
    "digest": {
     "type": "string"
    },
    "scheme": {
     "type": "string"
    },
    "signer": {
     "type": "string"
    },
    "source": {
     "type": "string"
    },
    "matches": {
     "type": "boolean"
    },
    "expected_signer": {
     "type": "string"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/touchstone-locomot-io-eip-191-signature-verification-ecrecover-a97e7ba9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from touchstone.locomot.io](https://www.zero.xyz/host/touchstone.locomot.io/llms.txt)