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Signature insights

Flask Only
This feature is experimental and only available in MetaMask Flask, the canary distribution of MetaMask.

You can provide signature insights before a user signs a message. For example, you can warn the user about potentially dangerous signature requests.


1. Request permission to display signature insights

Request the endowment:signature-insight permission by adding the following to your Snap's manifest file:

"initialPermissions": {
"endowment:signature-insight": {}

If you need to receive the origin of the signature request, add allowSignatureOrigin to the permission object, and set it to true:

"initialPermissions": {
"endowment:signature-insight": {
"allowSignatureOrigin": true

2. Implement the onSignature entry point

Expose an onSignature entry point, which receives a signature object. The shape of this object depends on the chain and the signing method used. This is why it's typed as Record<string, unknown>.

For Ethereum and Ethereum-compatible chains, the signature object can have one of the following shapes, depending on the signing method used:

interface EthSignature {
from: string
data: string
signatureMethod: "eth_sign"

Your Snap should use signatureMethod as the source of truth to identify the signature scheme it is providing insights for.

Once you've identified the signature object, your Snap can run any logic, including calling APIs. Then, your Snap must either return null if it has no insights to provide, or an object with a content property and an optional severity property as specified in the onSignature entry point.


Due to current MetaMask UI limitations, signature insights will only be displayed if your Snap's logic deems the signature to be one that a user shouldn't sign, that is, if you return a severity level of SeverityLevel.Critical.

The following is an example implementation of onSignature:

import type { OnSignatureHandler, SeverityLevel } from "@metamask/snaps-sdk";
import { panel, heading, text } from "@metamask/snaps-sdk";

export const onSignature: OnSignatureHandler = async ({
}) => {
const insights = /* Get insights based on custom logic */;
return {
content: panel([
heading("My Signature Insights"),
text("Here are the insights:"),
...( => text(insight.value))),
severity: SeverityLevel.Critical,

When your Snap returns a signature insight with a severity of SeverityLevel.Critical, the custom UI displays in a modal after the user selects the Sign button. For example:

Signature insights warning


See the @metamask/signature-insights-example-snap package for a full example of implementing signature insights.