# Signature Caller Policy (/smart-accounts/permissions/policies/signature)

> For the complete documentation index, see [llms.txt](/llms.txt)



This is useful when you want the signer to sign messages for a set of particular protocols only.  For example, if you want to create a signer that can only sign USDC [permits](https://eips.ethereum.org/EIPS/eip-2612), then you can use this policy to ensure that only the USDC contract can validate its messages.

## API [#api]

```ts
import { toSignatureCallerPolicy } from "@zerodev/permissions/policies"

const signaturePolicy = toSignatureCallerPolicy({
  allowedCallers: [address1, address2]
})

const validator = toPermissionValidator(publicClient, {
  entryPoint,
  kernelVersion,
  signer: someSigner,
  policies: [
    signaturePolicy,
    // ...other policies
  ],
})
```

* `allowedCallers` is a list of addresses that are allowed to validate messages signed by the signer.