Zernio (formerly Late) API + MCP vs Mixpost API + MCP

Zernio (formerly Late) API + MCP

Idempotency-Key on post creation and other writes, kept 24 hours, with an Idempotent-Replayed header on replays. Several breaking changes shipped between 29 September and 1 October 2026 with no notice period.

Mixpost API + MCP

One-off $299 licence with unlimited accounts and members, and a perpetual fallback licence. No API or MCP in the free Lite edition.

Zernio (formerly Late) API + MCP

1. Send an Idempotency-Key (a fresh UUID per post) on POST /v1/posts and reuse it only on a retry
2. Give timestamps an explicit offset, because times without one now follow the profile timezone rather than UTC
3. Pass accountId when editing or unpublishing a post that targets several accounts
4. Wait Retry-After on 429. Analytics endpoints have their own per-second window
5. Call https://zernio.com/api/v1, not the old getlate.dev base, and pin the SDK version

Mixpost API + MCP

1. Call list-workspaces first. Workspace endpoints sit under /api/{workspaceUuid}
2. Check MIXPOST_CORE_PATH. It's empty by default from Pro v7 but defaults to mixpost in older versions and Lite
3. Create the token as a Viewer-role user when the agent only needs to read
4. Use unschedule-post rather than delete-post when a person wants a post pulled back to draft
5. Expect HTTP 422 with an errors.limit entry when a Cloud plan limit is hit