mcp-discord

discord_add_reaction

Add a bot reaction to Discord messages using emoji or custom emoji to respond to content or acknowledge interactions.

Instructions

Add a reaction from the bot to a message. Emoji can be a unicode glyph (e.g. "👍") or custom-emoji string ("name:id"). Requires Add Reactions + Read Message History.

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>",
      "message_id": "<message_id>",
      "emoji": "<emoji>"
    },
    "name": "discord_add_reaction"
  }
}

Input Schema

Name	Required	Description
`channel_id`	Yes
`message_id`	Yes
`emoji`	Yes	Unicode emoji or "name:id" for custom emoji.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Apr 23, 2026

TDQS

A4.4/5.0

Behavior4/5

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. It effectively describes the action (adding a reaction), specifies the actor (the bot), and outlines permission requirements. It also clarifies the emoji format, which is crucial for correct usage. However, it lacks details on rate limits, error conditions, or response format, leaving some behavioral aspects uncovered.

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 front-loaded with the core purpose, followed by essential details (emoji format and permissions) in a single, efficient sentence. Every part earns its place, with no redundant or verbose language, making it highly concise and well-structured.

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?

Given the tool's moderate complexity (3 parameters, no output schema, no annotations), the description is mostly complete. It covers the action, actor, parameters, and prerequisites. However, it lacks information on return values or error handling, which would be beneficial for full contextual understanding, especially without an output schema.

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

Parameters4/5

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

Schema description coverage is low (33%), with only the 'emoji' parameter documented in the schema. The description compensates by explaining the emoji format ('Unicode glyph or custom-emoji string') and implying the need for channel_id and message_id to target a specific message. This adds meaningful context beyond the bare schema, though it could further clarify parameter relationships or constraints.

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 specific action ('Add a reaction from the bot to a message') and resource ('message'), distinguishing it from sibling tools like discord_remove_reaction (which removes reactions) or discord_get_reactions (which retrieves them). The verb 'Add' is precise and the target 'reaction from the bot' is well-defined.

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

Usage Guidelines4/5

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

The description provides clear context by specifying prerequisites ('Requires Add Reactions + Read Message History'), which helps determine when the tool can be used. However, it does not explicitly state when to use this tool versus alternatives like discord_remove_reaction or discord_get_reactions, nor does it mention exclusions or edge cases.

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