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slack-mcp-server

slack-mcp-server

by dudztroyer
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Remote

Add Slack Reaction

slack_add_reaction

Add a reaction emoji to a Slack message using channel (name or ID), message timestamp, and emoji name.

Instructions

Add a reaction emoji to a message. Accepts both channel names (#general, general) and channel IDs (C1234567890).

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>",
      "timestamp": "<timestamp>",
      "reaction": "<reaction>"
    },
    "name": "slack_add_reaction"
  }
}

Input Schema

NameRequiredDescriptionDefault
channelYesThe channel name (e.g., #general, general) or channel ID (e.g., C1234567890) containing the message
timestampYesThe timestamp of the message to react to
reactionYesThe name of the emoji reaction (without ::)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.0.5

TDQS

A3.6/5.0
Behavior3/5

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

Given no annotations, the description carries full burden. It mentions both channel name and ID acceptance but lacks details on effects (e.g., idempotency, error behavior) which is minimal but acceptable for a simple action.

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 concise sentences with no fluff. Every part adds value, front-loaded with the core purpose.

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

Completeness4/5

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

For a simple tool with 3 required parameters and no output schema, the description covers the purpose and parameter format adequately. Lack of return value or error info is a minor gap.

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 description adds no new meaning beyond what the schema already provides. Baseline of 3 is appropriate.

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 action 'Add a reaction emoji to a message' with a specific verb and resource. It distinguishes from sibling tools which focus on getting channels, messages, or profiles.

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?

No guidance on when to use this tool versus alternatives. The description simply states what it does without context on prerequisites, limitations, or alternative tools.

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

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