mcp-saas-toolkit

slack_send_message

Send messages to Slack channels or DMs. Supports Markdown formatting and thread replies.

Instructions

Send a message to a Slack channel or DM. Supports plain text, Markdown (mrkdwn), and thread replies.

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": "<channel>",
      "text": "<text>"
    },
    "name": "slack_send_message"
  }
}

Input Schema

Name	Required	Description
`text`	Yes	Message text. Supports Slack mrkdwn formatting (bold, _italic_, `code`, etc.)
`channel`	Yes	Channel ID (e.g. C01234567) or channel name (e.g. #general). Channel ID is more reliable.
`thread_ts`	No	Timestamp of a parent message to reply in a thread
`unfurl_links`	No	Whether to unfurl link previews. Default: true

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jun 29, 2026

TDQS

A3.7/5.0

Behavior3/5

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

No annotations provided, so the description carries the burden. It indicates support for plain text, mrkdwn, and thread replies, but does not disclose potential side effects (e.g., rate limits, file size limits) or authentication requirements beyond the basic schema.

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?

Two sentences: first states purpose, second adds formatting/thread capability. No fluff, information dense, and front-loaded.

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?

With no output schema, the description does not explain return values (e.g., message timestamp). For a messaging tool, this is a minor gap but acceptable given the simplicity and common API understanding.

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 documents all parameters. The description adds no additional meaning beyond what is in the schema, meeting the baseline.

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

Purpose5/5

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

The description clearly states the verb 'Send' and the resource 'a message to a Slack channel or DM', and distinguishes from siblings like slack_add_reaction or slack_list_channels by specifying the core messaging functionality.

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

Usage Guidelines3/5

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

The description does not provide explicit guidance on when to use this tool vs alternatives, but the purpose is self-evident. No exclusions or when-not-to-use conditions are mentioned.

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