The goals of eliminating schema creation during the creation of an analytics instrument and having a data contract between a data producer through to a Data Scientist are irreconcilable.

The first attempt at eliminating schema creation was to create the analytics/mediawiki/metrics_platform schema (AKA the monoschema). The monoschema contains many optional "Core Fields" – properties that are used relatively frequently in analytics instruments – and a custom_data property, which can contain arbitrary amounts of data that don't fit into those Core Fields. Using the monoschema in your instrument means that you don't have to create a new schema but also that there's no data contract between your instrument (the data producer) and the Data Scientist.

We can, however, minimise schema creation by providing a set of schemas and/or schema fragments that represent "Core Interactions" – interactions that are frequently instrumented, e.g.

1. The user entering/exiting a funnel
2. The user seeing a UI element
3. The user tapping/clicking a UI element
4. …

Further, for each Core Interaction schema that we provide, we can create a corresponding API and protocol for submitting an event that can be validated with that schema, e.g.

type Token = string;

interface ScopedEventSubmitter {
	readonly funnelEntryToken: Token;

	submitClick( elementID: string, elementFriendlyName?: string ): void;
}

interface MetricsPlatform {

	/**
	 * Creates an event submitter that submits events to the stream. All
	 * submitted events will have the `funnel_entry_token` property set.
	 *
	 * Before the event submitter is returned, a `funnel_enter` event
	 * representing the user entering the funnel is submitted.
	 */
	enterFunnel( streamName: string, funnelEntryToken?: Token ): ScopedEventSubmitter;

	getEnteredFunnels(): string[];
}

namespace mw {
	export metricsPlatform: MetricsPlatform;
}

// ---

const PAGEVIEW_TOKEN: Token = mw.user.getPageviewToken();

const submitter = mw.metricsPlatform.enterFunnel( 'mediawiki.ui.clicks', PAGEVIEW_TOKEN );

// Later...
submitter.submitClick( 'pt-notifications-alert', 'notifications' );