Versioning approach

The Merion API does not currently use version prefixes in endpoint URLs (e.g. /v1/). The API surface is stable by design — changes are additive where possible.

Breaking changes are communicated via this changelog and via direct email notification to registered integrators (see below). Non-breaking additions — new optional request fields, new response fields, new endpoints — are made without a version change and without advance notice, though they will appear in this changelog.

Breaking vs non-breaking changes

Breaking changes (communicated in advance)

Removing an endpoint
Removing a required or optional field from a request or response
Changing the type of an existing field (e.g. string to number)
Changing the semantic meaning of an existing field
Changing error codes or status codes for existing conditions
Reducing rate limits (treated as breaking — registered integrators will be notified in advance)

Non-breaking changes (may occur without advance notice)

Adding a new optional request field
Adding a new field to an existing response (your deserialiser should ignore unknown fields)
Adding a new endpoint
Adding a new form key to POST /public/forms/{key}
Documentation improvements with no API change

Change history

2026-06-29

Documentation expanded — no breaking API changes. Added eight new guide pages to developers.merion.com.au: Authentication (full OIDC/PKCE walkthrough), Forms API Recipes, Errors & Rate Limits, OpenAPI Specification, Discovery & Well-Known, Integration Checklist, SDK & Tools, and this changelog. Five new on-brand SVG diagrams added: OIDC auth flow, request/response envelope, error-handling flow, OpenAPI workflow, and integration phases.

2026-03-01

Initial public API documentation published at developers.merion.com.au. Covered: overview, getting started, API reference, forms API, webhooks, status and support.

Registering your integration

If you are an integrator relying on the Merion API, register your integration by emailing [email protected] with the subject line "API Integration Registration". Include:

Your name and organisation.
The endpoints and form keys you rely on.
A contact email for change notifications.

Registered integrators receive advance notice of breaking changes — typically at least four weeks before the change is deployed, more for significant changes.

Feedback

If you encounter undocumented behaviour, believe something in the docs is incorrect, or have a suggestion for the API, email [email protected]. The Merion team aims to respond within two business days.

Changelog & Versioning