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Current version

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

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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.

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Change categories

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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

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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)

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Staying updated

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

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MCP protocol version

MCP clients should send protocolVersion: "2025-03-26" (or newer supported) in initialize. See MCP Server.