Slack MCP Server

slack_post_message

Post messages to Slack channels using channel IDs and text content to facilitate team communication and updates.

Instructions

Slack 채널에 새 메시지 게시

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "channel_id": "<channel_id>",
      "text": "<text>"
    },
    "name": "slack_post_message"
  }
}

Input Schema

Name	Required	Description	Default
`channel_id`	Yes	메시지를 게시할 채널의 ID
`text`	Yes	게시할 메시지 내용

Schema Changelog

Changes observed during successful MCP inspections.

First observedJan 28, 2026

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 full burden for behavioral disclosure. While '게시' (post) implies a write operation, it doesn't specify permissions needed, rate limits, whether the message is ephemeral or permanent, or what happens on failure. This is inadequate for a mutation tool with zero annotation coverage.

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 in Korean that directly states the tool's purpose with zero wasted words. It's appropriately sized and front-loaded, making it easy for an agent to parse quickly.

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 cover behavioral aspects like authentication requirements, error handling, or response format. Given the complexity of posting to Slack (which involves permissions, formatting options, 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?

Schema description coverage is 100%, so the schema already fully documents both parameters (channel_id and text). The description adds no additional parameter information beyond what's in the schema, such as format examples or constraints. Baseline 3 is appropriate when schema does all the work.

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 ('게시' meaning 'post') and resource ('Slack 채널에 새 메시지' meaning 'new message to Slack channel'), providing a specific verb+resource combination. However, it doesn't differentiate from sibling tools like slack_reply_to_thread or slack_add_reaction, which also involve posting content to Slack.

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. It doesn't mention when to use slack_post_message versus slack_reply_to_thread for threaded replies, or slack_add_reaction for reactions, leaving the agent without context for tool selection.

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

Deploy Server