# Post Slack ephemeral message

Canonical URL: https://docs.fuse.init.inc/integrations/slack/actions/messages.post_ephemeral

Post an ephemeral message visible only to one user in a channel. Delivery requires the user to be in the channel; ephemeral messages are not durable.

Action ID: `messages.post_ephemeral`
Provider: Slack (`slack`)
Contract version: 1

## Risk and exposure

- Risk: Write
- Idempotency: Unsafe — Retries may duplicate side effects; callers must coordinate carefully.
- Availability: Default
- Exposure: REST, SDK, MCP
- MCP hints: readOnly=false, destructive=false, idempotent=false, openWorld=true

## Required scopes

- `chat:write`

## Input schema fields

- `channel_id`
- `user_id`
- `text`
- `thread_ts`

## Output schema fields

- `channel_id`
- `message_ts`

Provider overview: https://docs.fuse.init.inc/integrations/slack
Actions index: https://docs.fuse.init.inc/integrations/slack/actions
Exact canonical JSON contract: https://docs.fuse.init.inc/api/catalog/v1/providers/slack/actions/messages.post_ephemeral
Deployment-effective discovery: https://api.fuse.init.inc/v1/tenants/%7Btenant_id%7D/providers/slack/actions