OpenWA MCP Server

react_to_message

Send an emoji reaction to a WhatsApp message. Input session, chat, and message IDs.

Instructions

React to a specific WhatsApp message 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>",
      "chatId": "<chatId>",
      "messageId": "<messageId>",
      "reaction": "<reaction>"
    },
    "name": "react_to_message"
  }
}

Input Schema

Name	Required	Description
`sessionId`	Yes	Session ID
`chatId`	Yes	Chat ID containing the message
`messageId`	Yes	ID of the message to react to
`reaction`	Yes	Emoji reaction (e.g. 👍, ❤️, 😂)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0May 19, 2026

TDQS

A3.8/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. While it describes the basic action (reacting with an emoji), it lacks details on whether the reaction is reversible, visible to others, or requires the message to exist. This is minimal but not contradictory.

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, concise sentence with no fluff. Every word earns its place.

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 action with four parameters and no output schema, the description covers the essential purpose. It could be improved by noting that the reaction must be a valid emoji, but it is generally adequate.

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%. The description's mention of emoji examples adds little beyond the schema's parameter descriptions. 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 verb 'react', the resource 'specific WhatsApp message', and the means 'with an emoji'. It is distinct from sibling tools like delete_message or send_text.

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?

No explicit guidance on when to use this tool versus alternatives. The purpose is evident, but the description does not provide context for when not to use it (e.g., for system messages).

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