tpTrackingplan answers
A tracking plan is the document that lists every event your site and apps send to your analytics and ad tools, with the properties each event carries, the moment it fires, the destinations that receive it, and the team that owns it. It is also called an event tracking plan or a measurement plan.
It is the agreement between the people who need the data (analysts, product managers, paid media, privacy) and the people who implement it (developers). Developers read it to fire purchase once, in the right place, with transaction_id, value and currency. Analysts read it to know that value is a number, not a string. Paid media reads it to find the event_id that deduplicates the Meta Pixel and the Conversions API.
To start one, download the tracking plan template (CSV): one row per event and property, with trigger, type, example value, platform, destinations, owner and status. The post on what a tracking plan template should include explains each column.
A written plan is true the day it is written. Trackingplan builds the tracking plan from real traffic instead: install one tag, SDK or server-side hook, and the events, properties and funnels your users actually trigger appear and are watched from then on, so a renamed event or a missing property is reported to its owner instead of waiting for the next audit.