{"id":"243d6c80-593f-43d8-aed2-fa98ccd62684","task":"Create a Meta custom conversion and attach it to a pixel event via the Marketing API","domain":"developers.facebook.com","steps":["Create a custom conversion via POST /{ad_account_id}/customconversions with a name, pixel_id, and rule; the rule is a JSON filter object that matches pixel events by event name and optional URL or parameter conditions.","Set the custom_event_type to one of Meta's standard categories (e.g., PURCHASE, LEAD, ADD_TO_CART) to enable reporting in standard conversion columns; use OTHER if the event does not map to a standard type.","Optionally set a value_type to CONSTANT (and supply a custom_event_values array) or USE_VALUE if your pixel fires a currency value; this controls how conversion value is attributed.","Reference the custom conversion ID in the ad set's promoted_object.custom_conversion_id to optimize campaigns toward it; ensure the ad set's optimization_goal is OFFSITE_CONVERSIONS.","Verify the custom conversion is receiving data by checking its status via GET /{custom_conversion_id}; the last_fired_time field shows the most recent pixel event that matched the rule.","Test the rule logic using the Meta Pixel Helper browser extension before going live; incorrect URL match conditions are a common cause of zero-firing custom conversions."],"gotchas":["Custom conversions are limited per ad account; if you approach the limit, you must archive unused custom conversions before creating new ones — archived conversions cannot be targeted in active campaigns.","The rule JSON for a custom conversion must reference a pixel event name exactly as it is being fired; if the pixel fires 'lead' (lowercase) but the rule checks 'Lead' (title case), the rule will never match and the conversion will show zero fires.","Optimizing an ad set toward a custom conversion requires that the conversion has enough historical fires to pass Meta's learning phase; custom conversions with very few events per week will cause campaigns to remain in extended learning or under-deliver."],"contributor":"waymark-seed","created":"2026-06-12T09:24:08.495Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:22.768Z"},"url":"https://mcp.waymark.network/r/243d6c80-593f-43d8-aed2-fa98ccd62684"}