channel

Invoke a channel action — Slack send_message, open_modal, add_reaction, … — without going through an agent turn.

Source	internal/agents/workflow/nodes/channel.go
When to use	Send messages, open modals, react, reply via Slack / Telegram / etc. Use over connector when the action is channel-flavoured (interactive surfaces, response_url, App Home).
Discovery	workflow_integration MCP op returns the full per-channel event + action catalog with input_schema / output_schema per action.

Schema

Field	Type	Required	Notes
channel	string	✅	Channel adapter key (slack, telegram, …).
op	string	✅	Action key registered by the adapter.
args	map (templated)		Per-action input. Field set comes from the action's input_schema.
arg_modes	map		Per-arg fixed / expression.

Output

Field	Type	What (action-dependent)
ts	string	Slack: message timestamp.
channel	string	Channel ID the action landed in.
view_id	string	open_modal only.
view_hash	string	open_modal only.

Per-action output schemas are in workflow_integration — call it for the exact shape.

Slack action registry

Action	What
send_message	Post a message in a channel / DM / thread, with optional Block Kit blocks.
update_message	Edit an existing message by ts.
send_ephemeral	Visible only to one user.
add_reaction	Emoji reaction.
open_dm	Open (or reuse) a DM channel with a user, returning the channel ID.
open_modal, push_modal, update_modal	Open / push / update a Slack modal (uses trigger_id from an interaction payload).
publish_home	Update a user's App Home tab.
respond_url	Reply to an interaction using its response_url (works even when the bot lacks chat:write on that channel).

See Channels ▶ Slack for the transport details these actions ride on.

Example

{
  "id": "send_reply",
  "type": "channel",
  "channel": "slack",
  "op": "send_message",
  "arg_modes": {
    "channel": "expression",
    "text": "expression"
  },
  "args": {
    "channel": "{{index .Event.Payload \"channel_id\"}}",
    "text": "Got it, looking into {{.Node.classify.verdict}}.",
    "thread_ts": "{{index .Event.Payload \"thread_ts\"}}"
  }
}

Pair with

• agent — agent generates the reply, channel posts it.
• connector — for raw Slack Web API calls without channel-side hooks.