Sending Messages

slackblocks produces the JSON payloads that Slack APIs accept; it does not make HTTP calls itself. Send those payloads with the established Slack client for your language or any HTTP client.

The trick is the ** operator: a slackblocks.Message is a mapping, so you can unpack it directly into client.chat_postMessage(...).

With the modern slack-sdk

Python (slackblocks)

from os import environ
from slack_sdk import WebClient
from slackblocks import Message, SectionBlock


client = WebClient(token=environ["SLACK_API_TOKEN"])
block = SectionBlock("Hello, world!")
message = Message(channel="#general", blocks=block)

response = client.chat_postMessage(**message)

JSON Message

{
    "channel": "#general",
    "mrkdwn": true,
    "blocks": [
        {
            "type": "section",
            "block_id": "992ceb6b-9ad4-496b-b8e6-1bd8a632e8b3",
            "text": {
                "type": "mrkdwn",
                "text": "Hello, world!"
            }
        }
    ]
}

Note: the block_id field is a pseudorandomly generated UUID. Pass an explicit block_id to any block constructor if you need deterministic IDs (e.g. for testing or interaction handling).

Equivalent `curl`

curl -H "Content-type: application/json" \
  --data '{"channel":"#general","blocks":[{"type":"section","block_id":"992ceb6b-9ad4-496b-b8e6-1bd8a632e8b3","text":{"type":"mrkdwn","text":"Hello, world!"}}]}' \
  -H "Authorization: Bearer ${SLACK_API_TOKEN}" \
  -X POST https://slack.com/api/chat.postMessage

Slack UI

With the legacy slackclient

The API is identical — only the import path changes:

from os import environ
from slack import WebClient   # legacy slackclient package
from slackblocks import Message, SectionBlock


client = WebClient(token=environ["SLACK_API_TOKEN"])
message = Message(channel="#general", blocks=SectionBlock("Hello, world!"))

response = client.chat_postMessage(**message)

Other delivery surfaces

slackblocks provides specialized message classes for each Slack delivery surface. They all unpack the same way as Message.

Incoming webhooks

from slack_sdk.webhook import WebhookClient
from slackblocks import WebhookMessage, SectionBlock

webhook = WebhookClient(url="https://hooks.slack.com/services/...")
message = WebhookMessage(blocks=SectionBlock("Build complete :white_check_mark:"))

webhook.send(**message)

WebhookMessage supports webhook-only options like response_type, replace_original, and delete_original.

Slash command / interaction responses

When responding to a slash command or interactive payload, use MessageResponse:

from slackblocks import MessageResponse, SectionBlock

response_body = MessageResponse(
    blocks=SectionBlock("Got it! Working on that now..."),
    ephemeral=True,        # only visible to the invoking user
).json()

Modals & home tabs

For modals and home tab views, build a Modal (or HomeTabView) and pass it to views_open / views_publish:

from slack_sdk import WebClient
from slackblocks import Modal, SectionBlock

client = WebClient(token=environ["SLACK_API_TOKEN"])
modal = Modal(
    title="Confirm action",
    blocks=[SectionBlock("Are you sure?")],
    submit="Yes",
    close="Cancel",
)

client.views_open(trigger_id=trigger_id, view=modal.to_dict())

See Modals reference and Views reference for the full surface.

Sending without an SDK

Because Message renders to a plain dict, you can also send it directly:

import json
import os
import urllib.request

from slackblocks import Message, SectionBlock

message = Message(channel="#general", blocks=SectionBlock("Hello, world!"))

req = urllib.request.Request(
    "https://slack.com/api/chat.postMessage",
    data=message.json().encode("utf-8"),
    headers={
        "Content-Type": "application/json; charset=utf-8",
        "Authorization": f"Bearer {os.environ['SLACK_API_TOKEN']}",
    },
)
urllib.request.urlopen(req)