Slack Web API
Browse all Slack APIs✓ Official Vendor SpecCommunicationsChat Messagingoauth2169 EndpointsREST
For Agents
Post messages, manage channels, query conversations, and administer Slack workspaces. Supports 169 endpoints covering messaging, file uploads, user management, and workspace administration with OAuth 2.0 scopes.
Use for: I need to post a message to a Slack channel, Search for messages mentioning a specific topic in the last week, I want to create a new private channel and invite team members, Upload a file to a channel with a descriptive comment
Not supported: Does not handle video calls, project management, or email delivery — use for team messaging, channel management, and file sharing only.
Send messages, manage channels, upload files, and administer workspaces through 169 HTTP RPC-style endpoints. Supports real-time messaging, threaded conversations, emoji reactions, file sharing, user group management, app installation administration, and granular OAuth 2.0 scope-based permissions across Slack workspaces.
Install Jentic One Beta
Connect the Slack Web API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Slack Web API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Slack Web API.
Post messages to channels and threads with rich formatting, blocks, and attachments
Search messages across channels by keyword, date range, and sender
Upload and share files with preview generation and access control
Manage channel lifecycle including creation, archiving, topic setting, and membership
Administer workspace-level settings, emoji, user groups, and app permissions
React to messages with emoji and pin important messages for team reference
Configure Do Not Disturb schedules and query team availability status
Use Cases
Patterns agents use Slack Web API for, with concrete tasks.
★ AI Agent Messaging Automation
AI agents use the Slack Web API through Jentic to post structured notifications, status updates, and alerts to team channels without manual setup. An agent searches for the message posting operation, loads the schema with blocks and attachments, and executes delivery in under a minute. This powers incident alerts, deployment notifications, daily standup summaries, and automated customer escalation routing.
Post a message to channel C0123456 with text 'Deployment v2.4.0 completed' and a blocks array containing a section with a green checkmark emoji and deployment details
Channel and Conversation Management
Create, archive, and configure channels programmatically to support team workflows. The Slack Web API provides 169 endpoints for setting channel topics, managing membership, adjusting posting permissions, and bulk-archiving stale channels. Organizations use this to enforce naming conventions, auto-create project channels, and maintain workspace hygiene at scale.
Create a private channel named 'proj-alpha-2026' with topic 'Project Alpha coordination', then invite user IDs U111, U222, and U333
Cross-Channel Message Search and Analytics
Search messages across all accessible channels by keyword, sender, date range, and channel. The Slack search endpoints return matched messages with context, highlighting, and pagination. Teams use this for compliance audits, knowledge retrieval, and building internal search tools that surface relevant conversations without manual browsing.
Search for messages containing 'outage' posted in the last 48 hours across all channels and return the top 10 matches with channel name, sender, and timestamp
File Sharing and Document Distribution
Upload files to channels or direct messages with automatic preview generation and access controls. The Slack Web API handles file upload via external URLs or direct binary upload, generates previews for common formats, and manages file permissions. This enables automated report distribution, log file sharing from CI/CD, and document collaboration workflows.
Upload a CSV file to channel C0123456 using files.getUploadURLExternal followed by files.completeUploadExternal with initial_comment 'Weekly sales report attached'
Key Endpoints
169 endpoints — send messages, manage channels, upload files, and administer workspaces through 169 http rpc-style endpoints.
METHOD
PATH
DESCRIPTION
POST
/chat.postMessage
Post a message to a channel
GET
/conversations.history
Fetch message history for a channel
POST
/conversations.create
Create a new channel
GET
/search.messages
Search messages across channels
POST
/files.getUploadURLExternal
Get upload URL for a file
POST
/conversations.invite
Invite users to a channel
POST
/reactions.add
Add an emoji reaction to a message
GET
/users.list
List all workspace users
POST
/chat.postMessage
Post a message to a channel
GET
/conversations.history
Fetch message history for a channel
POST
/conversations.create
Create a new channel
GET
/search.messages
Search messages across channels
POST
/files.getUploadURLExternal
Get upload URL for a file
POST
/conversations.invite
Invite users to a channel
POST
/reactions.add
Add an emoji reaction to a message
GET
/users.list
List all workspace users
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
Slack OAuth 2.0 bot and user tokens are stored encrypted in the Jentic MAXsystem vault. Agents receive pre-scoped tokens matching the required OAuth scopes — raw xoxb/xoxp tokens never enter the agent context.
Intent-based discovery
Agents search by intent (e.g., 'post a message to a Slack channel') and Jentic returns matching operations from the 169-endpoint spec with their OAuth scope requirements and parameter schemas, so agents call the right method without navigating Slack's extensive API docs.
Time to first call
Direct Slack integration: 3-5 days for OAuth app setup, scope configuration, and event subscription handling. Through Jentic: under 1 hour — search, load schema, execute.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using Slack Web API through Jentic.
What authentication does the Slack Web API use?
The Slack Web API uses OAuth 2.0 with granular scopes. Bot tokens (xoxb-) and user tokens (xoxp-) authorize different operation sets. Each endpoint requires specific OAuth scopes listed in the spec. Through Jentic, OAuth tokens are stored encrypted in the MAXsystem vault — agents receive pre-scoped tokens without managing the OAuth flow themselves.
Can I post messages with rich formatting using the Slack Web API?
Yes. The chat.postMessage endpoint accepts a blocks array using Slack's Block Kit format. You can include sections with markdown text, images, buttons, select menus, and dividers. Alternatively, use the text parameter with Slack's mrkdwn syntax for simpler formatting. The blocks array supports up to 50 blocks per message.
What are the rate limits for the Slack Web API?
Slack uses tiered rate limiting. Most methods allow 1 request per second (Tier 2) or 50+ per minute (Tier 3). chat.postMessage allows about 1 message per second per channel. Responses include Retry-After headers when limits are exceeded. Web API methods are classified into tiers 1-4 with increasing generosity.
How do I search for messages across channels through Jentic?
Search Jentic for 'search Slack messages'. Jentic returns the GET /search.messages endpoint schema with query, sort, and sort_dir parameters. The query parameter supports Slack search modifiers like 'from:@user', 'in:#channel', 'before:2026-05-01'. Load the schema, set your query, and execute to get paginated results.
Can I create channels and manage membership via the API?
Yes. Use conversations.create with a name and is_private flag to create channels. Then conversations.invite adds users by their user IDs. conversations.setTopic and conversations.setPurpose configure the channel metadata. conversations.kick removes members, and conversations.archive retires unused channels.
How do I upload files to Slack channels?
Use the two-step upload flow: first call files.getUploadURLExternal to get a presigned upload URL and file_id, then upload the binary data to that URL, and finally call files.completeUploadExternal with the file_id and channel_id to publish it. This replaced the older files.upload endpoint and supports files up to 1GB.
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