> ## Documentation Index
> Fetch the complete documentation index at: https://docs.echozero.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Versioning policy

> How EchoZero versions the REST API and announces breaking changes.

## Current version

The public REST API is **`v1`** (`/api/v1/...`). The OpenAPI document version tracks the deployment (`1.0` in `docs-json`).

## Signal schema version

Structured signal envelopes include optional `version` (currently **`1`**, issue `#1098`). New event types and fields are additive within the same major version.

## Change categories

| Type           | Policy                                                                                                   |
| -------------- | -------------------------------------------------------------------------------------------------------- |
| **Additive**   | New endpoints, optional JSON fields, new enum values: no notice required                                 |
| **Behavioral** | Execution rule changes: announced in [Changelog](/changelog)                                             |
| **Breaking**   | Removed fields, renamed paths, auth changes: 30-day notice in changelog + email to registered developers |

## What we consider breaking

* Removing or renaming a published `/v1` path
* Requiring a previously optional field on inbound signals
* Changing HMAC signing algorithms without a new header/version
* Tightening default rate limits below published tiers

## What is not breaking

* New `skipReason` or error codes
* New MCP tools or scopes (existing keys keep working)
* Internal admin endpoint changes (not in public OpenAPI)

## Staying updated

* [Changelog](/changelog) (dated entries)
* `GET https://mcp.echozero.app/api/docs-json` (machine-readable)
* Register in the Dev Portal for operational emails

## MCP protocol version

MCP clients should send `protocolVersion: "2025-03-26"` (or newer supported) in `initialize`. See [MCP Server](/guides/mcp).