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Slack MCP Server

by AVIMBU

Slack Model Context Protocol Server

This is a connector to allow Claude Desktop (or any MCP client) to interact with your Slack workspace to post messages and query a list of all users.

Local Development

In order to run this client locally, add the following configuration to your Claude Desktop MCP Server config file:

 {
  "mcpServers": {
    "mcp-slack-local": {
      "command": "node",
      "args": ["/path/to/project/dist/index.js"], <---- replace this with your project path
      "env": {
        "SLACK_BOT_USER_OAUTH_TOKEN": "test-bot-token", 
        "SLACK_TEAM_ID": "test-team-id"
      }
    },
  }
}

After this, you should be able to test this implementation in your Claude Desktop App using example prompts like:

  • "Can you list all users of my Slack team?"

  • "Can you send a welcome message to my Slack Channel with the ID <channel id>?"

Running the server locally:

node dist/index.js

With the build in another terminal

npm run watch

Related MCP server: Slack MCP Server by CData

Slack Permission Scopes

The following permissions are already implemented:

Permission

Description

Implemented

app_configurations:read

Read app configuration info via App Manifest APIs

❌

app_configurations:write

Write app configuration info and create apps via App Manifest APIs

❌

app_mentions:read

View messages that directly mention @your_slack_app in conversations that the app is in

❌

assistant:write

Allow your slack app to act as an AI Assistant

❌

bookmarks:read

List bookmarks

❌

bookmarks:write

Create, edit, and remove bookmarks

❌

calls:read

View information about ongoing and past calls

❌

calls:write

Start and manage calls in a workspace

❌

canvases:read

your slack app will be able to access contents of canvases created inside Slack.

❌

canvases:write

your slack app will be able to create, edit and remove canvases.

❌

channels:history

View messages and other content in public channels that your slack app has been added to

❌

channels:join

Join public channels in a workspace

❌

channels:manage

Manage public channels that your slack app has been added to and create new ones

❌

channels:read

View basic information about public channels in a workspace

❌

channels:write.invites

Invite members to public channels

❌

channels:write.topic

Set the description of public channels

❌

chat:write

Post messages in approved channels & conversations

✅

chat:write.customize

Send messages as @your_slack_app with a customized username and avatar

❌

chat:write.public

Send messages to channels @your_slack_app isn't a member of

❌

commands

Add shortcuts and/or slash commands that people can use

❌

conversations.connect:manage

Allows your slack app to manage Slack Connect channels

❌

conversations.connect:read

Receive Slack Connect invite events sent to the channels your slack app is in

❌

conversations.connect:write

Create Slack Connect invitations for channels that your slack app has been added to, and accept invitations sent to your slack app

❌

datastore:read

View and see data from Slack App Datastore

❌

datastore:write

Write data to Slack App Datastore

❌

dnd:read

View Do Not Disturb settings for people in a workspace

❌

emoji:read

View custom emoji in a workspace

❌

files:read

View files shared in channels and conversations that your slack app has been added to

❌

files:write

Upload, edit, and delete files as your slack app

❌

groups:history

View messages and other content in private channels that your slack app has been added to

❌

groups:read

View basic information about private channels that your slack app has been added to

❌

groups:write

Manage private channels that your slack app has been added to and create new ones

❌

groups:write.invites

Invite members to private channels

❌

groups:write.topic

Set the description of private channels

❌

im:history

View messages and other content in direct messages that your slack app has been added to

❌

im:read

View basic information about direct messages that your slack app has been added to

❌

im:write

Start direct messages with people

❌

im:write.topic

Set the description in direct messages

❌

incoming-webhook

Create one-way webhooks to post messages to a specific channel

❌

links.embed:write

Embed video player URLs in messages and app surfaces

❌

links:read

View URLs in messages

❌

links:write

Show previews of URLs in messages

❌

metadata.message:read

Allows your slack app to read message metadata in channels that your slack app has been added to

❌

mpim:history

View messages and other content in group direct messages that your slack app has been added to

❌

mpim:read

View basic information about group direct messages that your slack app has been added to

❌

mpim:write

Start group direct messages with people

❌

mpim:write.topic

Set the description in group direct messages

❌

none

Execute methods without needing a scope

❌

pins:read

View pinned content in channels and conversations that your slack app has been added to

❌

pins:write

Add and remove pinned messages and files

❌

reactions:read

View emoji reactions and their associated content in channels and conversations that your slack app has been added to

❌

reactions:write

Add and edit emoji reactions

❌

reminders:read

View reminders created by your slack app

❌

reminders:write

Add, remove, or mark reminders as complete

❌

remote_files:read

View remote files added by the app in a workspace

❌

remote_files:share

Share remote files on a user's behalf

❌

remote_files:write

Add, edit, and delete remote files on a user's behalf

❌

search:read.files

Search a workspace's content in files

❌

search:read.im

Search a workspace's content in direct messages

❌

search:read.mpim

Search a workspace's content in group direct messages

❌

search:read.private

Search a workspace's content in private channels

❌

search:read.public

Search a workspace's content in public channels

❌

team.billing:read

Allows your slack app to read the billing plan for workspaces your slack app has been installed to

❌

team.preferences:read

Allows your slack app to read the preferences for workspaces your slack app has been installed to

❌

team:read

View the name, email domain, and icon for workspaces your slack app is connected to

❌

tokens.basic

Execute methods without needing a scope

❌

triggers:read

Read new Platform triggers

❌

triggers:write

Create new Platform triggers

❌

usergroups:read

View user groups in a workspace

❌

usergroups:write

Create and manage user groups

❌

users.profile:read

View profile details about people in a workspace

❌

users:read

View people in a workspace

✅

users:read.email

View email addresses of people in a workspace

❌

users:write

Set presence for your slack app

❌

workflow.steps:execute

Add steps that people can use in Workflow Builder

❌

workflows.templates:read

Read a workflow template

❌

workflows.templates:write

Write a workflow template

❌

Contact

If you have questions, feel free to contact us via AVIMBU.

Available Tools

2 tools
slack_get_usersB

Get a list of all users in the workspace with basic information

ParametersJSON Schema
NameRequiredDescriptionDefault
cursorNoPagination cursor for next page of results
limitNoMaximum number of users to return (default 100, max 200)

TDQS

B3.1/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. While it indicates this is a read operation ('Get'), it doesn't mention important behavioral aspects like authentication requirements, rate limits, error conditions, or what 'basic information' specifically includes. For a tool that presumably accesses workspace data, this leaves significant gaps in understanding how it behaves.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that communicates the core purpose without any wasted words. It's appropriately sized for a straightforward list operation and front-loads the essential information. Every word earns its place in this concise formulation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a relatively simple list operation with 2 parameters and no output schema, the description provides adequate but minimal context. It covers what the tool does but lacks important operational details like authentication requirements, rate limits, and what specific user information is returned. Without annotations or output schema, the description should ideally provide more complete guidance about the tool's behavior and results.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema description coverage is 100%, with both parameters ('cursor' and 'limit') fully documented in the schema. The description doesn't add any additional parameter semantics beyond what's already in the schema. According to the scoring rules, when schema coverage is high (>80%), the baseline is 3 even with no parameter information in the description.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb ('Get') and resource ('list of all users in the workspace'), making the purpose immediately understandable. It specifies 'with basic information' which adds useful context about the scope of returned data. However, it doesn't explicitly differentiate from the sibling tool 'slack_post_message', which is a completely different operation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. There's no mention of prerequisites, appropriate contexts, or comparison with the sibling 'slack_post_message' tool. The agent must infer usage purely from the tool name and description without any explicit guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

slack_post_messageC

Post a new message to a Slack channel

ParametersJSON Schema
NameRequiredDescriptionDefault
channel_idYesThe Channel ID to post the message to
textYesThe message text to post

TDQS

C2.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. While 'Post a new message' implies a write operation, it doesn't mention authentication requirements, rate limits, error conditions, or what happens if the channel doesn't exist. This leaves significant behavioral gaps for a mutation tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that communicates the core purpose without any wasted words. It's appropriately sized for a simple tool and gets straight to the point.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with no annotations and no output schema, the description is insufficient. It doesn't explain what the tool returns, error conditions, authentication requirements, or any behavioral details beyond the basic action. Given the complexity of posting to Slack (which involves permissions, formatting, etc.), more context is needed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage, with both parameters clearly documented in the schema. The description doesn't add any additional semantic context about the parameters beyond what's already in the schema, so it meets the baseline for high schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Post a new message') and target resource ('to a Slack channel'), making the purpose immediately understandable. However, it doesn't differentiate from its sibling tool 'slack_get_users' beyond the obvious difference in function, which is why it doesn't reach a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives or any prerequisites for usage. It simply states what the tool does without context about appropriate scenarios or limitations.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 2 tool updates
    • First observedslack_get_users
    • First observedslack_post_message

TDQS

B3.1/5.0

Scored across 2 tools

Disambiguation5/5

The two tools have clearly distinct purposes: one retrieves user information and the other posts messages, with no overlap in functionality. An agent can easily differentiate between them based on their descriptions.

Naming Consistency5/5

Both tools follow a consistent 'slack_verb_noun' pattern (slack_get_users, slack_post_message), using snake_case and clear action-object naming. This makes them predictable and easy to understand.

Tool Count2/5

With only 2 tools, the server feels severely under-scoped for a Slack integration, lacking essential operations like reading messages, managing channels, or handling reactions. This minimal set limits agent capabilities significantly.

Completeness2/5

The tool surface is highly incomplete for a Slack server, missing core functionalities such as reading channel messages, listing channels, updating or deleting messages, and interacting with threads. This will cause frequent agent failures in typical Slack workflows.

Maintenance

ActivityInactive
ResponsivenessNo issues

Related MCP Connectors

  • Enable interaction with Slack workspaces. Supports subscribing to Slack events through Resources.

  • WhatsMCP connects Claude and other MCP-compatible AI agents directly to WhatsApp. Send and receive text, images, documents, and voice notes; manage groups (create, add/remove members, promote admins); look up contacts and profiles; follow channels; and read call and message history — all through a standard MCP interface. For voice use cases, WhatsMCP offers SIP-based calling plans (inbound-only, or full inbound/outbound) so AI voice agents can answer and place WhatsApp calls, plus low-latency WebSocket integrations with voice agent providers like ElevenLabs. Multiple WhatsApp accounts can be paired and managed per workspace, with webhook support for real-time inbound message delivery to your own infrastructure.

  • Let Claude or ChatGPT search, read and send your WhatsApp messages over MCP. OAuth sign-in.

  • Talk to your public-facing AI from any MCP client — Claude, ChatGPT, Cursor, Cline, Windsurf.

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