What is actually involved
A webhook connector sends Tealium data out to an external endpoint over HTTP. Three pieces decide whether it delivers reliably: authentication (a static API key, OAuth, or signed headers, depending on the vendor), the action-and-parameter model that defines what the webhook can do and what values it requires, and helper functions for common transforms - hashing, formatting, conditional logic - so each connector isn't reinventing the same utility code.
When you need to build one by hand
Any outbound integration not covered by a pre-built connector - a bespoke internal system, a smaller or newer vendor, an internal data lake ingestion endpoint with its own auth scheme.
How to implement it properly
Confirm the destination's actual authentication requirement before building anything - a static key is the simplest and most durable option for a fire-and-forget connector; anything OAuth-based needs a token refresh strategy, which is more fragile in this context and should be planned for explicitly, not discovered in an incident. Define the action and its required parameters precisely against the destination's own API documentation. Use the connector platform's helper functions for common transforms rather than duplicating hashing or formatting logic per connector, which multiplies maintenance and inconsistency risk.
How to verify it worked
Send a deliberately malformed test payload and confirm the connector's failure and error handling behave as expected - does it retry, drop silently, or alert someone? A connector that only ever sees clean test payloads during setup has an unverified failure path, and failure paths are exactly where webhook incidents actually happen.
Named failure mode from our implementation audits: connector sprawl - destinations added for convenience over time, each one an unreviewed data recipient nobody re-checks after go-live.