Slack Send Message

Send messages to Slack channels or users from a workflow. Use it for notifications, alerts, bot replies, and any programmatic messaging in Slack.

When to Use

Use Slack Send Message when:

You need to post notifications or alerts to a Slack channel from a workflow
You want to reply in a thread after a Slack Trigger event
You need rich Block Kit messages with sections, buttons, or images
An AI Agent should send Slack notifications as a tool

Pair with Slack Trigger to receive events and reply in the same channel or thread.

Inputs

Handle	Type	Description
`input`	any	Upstream data for template expression references in settings bindings.

Output

Handle	Type	Description
`result`	object	Slack message send result

The result (accessed as {{ slack_message.* }}) shape:

Field	Type	Description
`success`	boolean	Whether the message was sent successfully
`message_ts`	string	Timestamp of the sent message (use as `thread_ts` for replies)
`channel`	string	Channel ID where the message was posted
`error`	string	Error message if `success` is `false`

{
  "success": true,
  "message_ts": "1719234567.123456",
  "channel": "C01234ABCDE",
  "error": null
}

Settings

Setting	Type	Default	Description
`channel`	string	—	Channel ID (e.g. `C01234ABCDE`) or name (e.g. `#general`). Required. Supports template expression bindings.
`text`	code editor	—	Message text content. Required. Supports template expression bindings.
`blocks`	code editor (JSON)	—	Optional Block Kit JSON array for rich formatting. When provided, takes priority over plain `text`. Supports template expression bindings.
`thread_ts`	string	—	Thread timestamp to reply in a thread. Supports template expression bindings.

Required Secrets

Configure on the Env Vars page:

Env Var	Description
`SLACK_BOT_TOKEN`	Bot User OAuth Token (`xoxb-...`) with `chat:write` scope. Create a Slack App at api.slack.com/apps, add the scope, install to your workspace, and copy the token.

Example

Canvas

Send a deployment alert to #alerts when a webhook fires:

Webhook Trigger → Slack Send Message

Slack Send Message settings:

Channel: #alerts
Message Text: Deployment succeeded for {{ webhook.body.service }} at {{ webhook.body.timestamp }}

Reply in a thread after a Slack Trigger:

Slack Trigger → Slack Send Message

Slack Send Message settings:

Channel: {{ slack.channel }}
Message Text: Got it! Processing your request...
Thread Timestamp: {{ slack.thread_ts }} (or {{ slack.timestamp }} for top-level replies)

Send a rich Block Kit message:

Channel: #alerts
Block Kit JSON:

[
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "*Deployment succeeded*\nService: `api-gateway`"
    }
  }
]

Access the result in downstream nodes:

{{ slack_message.success }}
{{ slack_message.message_ts }}
{{ slack_message.channel }}

TSL

import webhook from @tensorify/webhook-trigger:4.0.0
import slack from @tensorify/slack-send-message:1.0.0

node trigger @tensorify/webhook-trigger:4.0.0 {
    provider = "generic"
    path = "/deploy"
    method = "POST"
}

node notify @tensorify/slack-send-message:1.0.0 {
    channel = "#alerts"
    text = "Deployment succeeded for {{ webhook.body.service }}"
}

trigger.payload -> notify.input

Error Handling

Slack Send Message has an On Error control output branch. Enable it via the "Error output handle" toggle at the bottom of the settings panel.

The error branch fires when:

The Slack API returns an error (invalid channel, missing scope, rate limit, etc.)
SLACK_BOT_TOKEN is missing or invalid
Block Kit JSON is malformed

Connect the error output to a fallback notification, logging action, or If node. On the success path, check {{ slack_message.success }} — the node does not automatically stop execution on failure.

Common Gotchas

Channel access: The bot must be invited to the channel before it can post. Use /invite @your-bot in the channel.
Thread replies: Set thread_ts to the parent message's timestamp. Use {{ slack.timestamp }} or {{ slack.thread_ts }} from a Slack Trigger to reply in the same thread.
Block Kit vs text: When blocks is provided, it takes priority over plain text for message formatting.
Check slack_message.success: The node does not automatically stop execution on failure. Connect the On Error branch or add an If node to handle failures.
Missing SLACK_BOT_TOKEN: The node fails at runtime with an authentication error if the env var is not set.