Update a contact

PATCH /contacts/{address}

What you send is what changes. Everything you leave out stays as it was.

{ "properties": { "plan": "enterprise", "trial_ends": null } }

• A field you omit is left alone — this is the difference from POST, which replaces.
• properties is merged key by key, so the other merge fields survive.
• A merge field set to null is removed.

Returns the contact as it now stands. 404 not_found if the address is not on your list — PATCH does not create, because a typo in an address would otherwise quietly add a contact nobody meant.

Changing an address

You cannot. The address is the key, and an endpoint that changed it would be indistinguishable from a typo correcting the wrong person’s record. Create the new contact and delete the old one, with the consent it carried in mind — see deleting for why that matters.