I’m excited to share that we've added a consequential hint to the WebMCP spec! Here’s what you need to know about it:
For site devs: consequentialHint should be set to true when WebMCP tools may perform a high-stakes action: anything that might need explicit user permission in order to execute. If you’re going to make a purchase, send an email, or book travel, it would be beneficial to set this to true.
annotations: {
consequentialHint: true
}
For agent/model devs: the agent should regard this hint as a time to take a step back, ask for user verification- if there’s an alignment tool critic, it should be judging whether or not a consequential action is appropriate given the user’s request.
The interesting thing about hints like this, unlike other web specs, is that both the site and the agent have to get it right for this to work well. If one side exposes a hint and the other doesn’t honor it, it’s not doing much. And alternatively, if the site dev doesn’t expose but the agent is looking for it… you get it.
But combined, it’s powerful. It can create a safeguard against generating an action a user might not want or be expecting. And it gives more tools to developers to have precision in what should be occurring on their site. So the collective effect can keep users safer.