Create Meta Custom Conversion

Creates a custom conversion on a pixel. Rule: url_contains (visitors whose page URL contains this text, the classic thank-you / lead-page conversion), or event (a standard pixel event name), or BOTH (that event fired on that page). event must be a STANDARD Meta pixel event and is matched case-sensitively; any casing given is normalized: PageView, ViewContent, Search, AddToCart, AddToWishlist, InitiateCheckout, AddPaymentInfo, Purchase, Lead, CompleteRegistration, Contact, CustomizeProduct, Donate, FindLocation, Schedule, StartTrial, SubmitApplication, Subscribe. custom_event_type categorizes it for reporting/optimization (PURCHASE | LEAD | COMPLETE_REGISTRATION | ADD_TO_CART | CONTENT_VIEW | SEARCH | OTHER); without it, it is derived from the event. pixel_id from list_meta_pixels. confirm=false = preview.

An EVENT rule always carries a URL condition, because Meta rejects an event-only rule: without url_contains, an all-pages condition is added so the conversion means "this event anywhere on the site". custom_event_type must match the event; without it, it is set correctly automatically.

DELETING IS NOT POSSIBLE THROUGH THE API: Meta refuses custom-conversion deletion for this app (OAuthException 200), so a wrong one can only be removed by the user in Meta Events Manager → Custom conversions. confirm=false shows the exact name and rule before anything is created; every created conversion stays in the account (it can only be renamed, not deleted, from here).