Sending Messages

slackblocks produces the JSON payloads that the Slack APIs accept; it does not make HTTP calls itself. You're free to send the rendered messages with any HTTP client (curl, requests, httpx), but the recommended path is to combine slackblocks with the official slack-sdk (or its legacy slackclient predecessor).

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)JSON MessageEquivalent curlSlack UI

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)

{
    "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).

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

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)