What's the right way to fire Facebook Pixel standard/custom fbq events from GTM instead of hardcoding them?

Why this happens

Hardcoding fbq('track', ...) calls directly into page templates means every value has to be manually kept in sync with the page's actual state by whoever edits that template, and every future pixel change requires a code deploy instead of a container publish. Moving it into GTM, driven by dataLayer values pushed by the events that actually happen, decouples pixel configuration from page code the same way GA4 tagging already should be.

Fix it

1. Install the base pixel using GTM's Facebook Pixel template from the Template Gallery if your container does not already have it, configured to fire on All Pages (or gated behind consent) so fbq('init', ...) runs once per pageview.
2. For each standard event (Purchase, AddToCart, Lead, ViewContent), add a separate Facebook Pixel Standard Event tag, set the Standard Event type, and map its parameters to Data Layer Variables reading the same pushed values your GA4 tags already use.
3. Trigger each standard-event tag on the specific custom event pushed for that action, never on a generic page-level trigger, which would fire the event on every pageview rather than the actual action.
4. For events with no standard type, use fbq('trackCustom', ...) inside a Custom HTML tag, still triggered on a specific dataLayer custom event, and still reading dynamic values from Data Layer Variables rather than hardcoding them.
5. If you are also sending the same events via Conversions API, reuse the event_id pattern from the start of this build rather than retrofitting deduplication later - pass the same order-derived ID into both the GTM-fired client tag and your backend's CAPI payload.

How to verify it worked

In GTM Preview, trigger each action (add to cart, submit a lead form) and confirm the corresponding Pixel tag fires exactly once per action with the correct resolved parameter values in the tag's Variables tab. Cross-check in Meta Events Manager's Test Events tool that each event lands with the expected parameters and, for standard events, is correctly categorized under its standard event type.