wwebjs-mcp

message_react

Add an emoji reaction to a WhatsApp message by supplying chat ID, message ID, and session ID. Use an empty reaction string to remove the reaction.

Instructions

[Message] React with an emoji

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": {
      "sessionId": "<sessionId>"
    },
    "name": "message_react"
  }
}

Input Schema

Name	Required	Description
`chatId`	No	The chat id which contains the message
`reaction`	No	Emoji to react with. Send an empty string to remove the reaction.
`messageId`	No	Unique WhatsApp identifier for the message
`sessionId`	Yes	Unique identifier for the session (alphanumeric and - allowed)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 2, 2026

TDQS

C2.9/5.0

Behavior2/5

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

There are no annotations, so the description must disclose behavioral traits. It only says 'React with an emoji' and does not mention idempotency, that sending an empty string removes the reaction, or potential side effects like replacing an existing reaction. This is minimal behavioral disclosure.

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 short phrase that is immediately readable and front-loaded. It contains no filler, though its brevity leaves other dimensions under-served.

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 prerequisites (e.g., active session), behavior when the reaction is removed, or return values. It covers only the core action.

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% parameter coverage with detailed descriptions for all four parameters. The description adds no semantic value beyond what the schema already states—it merely restates the reaction concept.

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 uses the specific verb 'React' and identifies the emoji action, clearly differentiating this tool from message_forward, message_star, and message_reply. However, it omits the explicit object ('to a message'), relying on the [Message] prefix and tool name, so it is clear but not fully self-contained.

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 is given about when to use this tool vs alternatives such as message_getReactions (to view reactions) or message_star (a different message action). The description only states what the tool does, not when to choose it over siblings.

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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