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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.

TDQS

B3.1/5.0
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
ResponsivenessSyncing

Resources

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