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mcp-whatsapp

mcp-whatsapp

by Sealjay
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send_reaction

Idempotent

Add or remove an emoji reaction to an existing WhatsApp message. Provide the chat JID, message ID, and optional emoji; use empty string to clear the reaction.

Instructions

Add or replace an emoji reaction on an existing message; recipients see the small emoji badge attached to the original message. Reversible by calling again with an empty emoji string (clears the reaction); for a fresh message use send_message and for a quoted reply use send_reply. Returns the plain-text string Reaction sent on success.

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": {
      "chat_jid": "<chat_jid>",
      "message_id": "<message_id>"
    },
    "name": "send_reaction"
  }
}

Input Schema

NameRequiredDescriptionDefault
emojiNosingle emoji to react with; pass an empty string to clear an existing reaction
chat_jidYesWhatsApp JID: individual as `<digits>@s.whatsapp.net` or bare phone digits, group as `<digits>-<timestamp>@g.us`
message_idYesWhatsApp message ID of the target message (use `message_id` from list_messages)
sender_jidNoJID of the original sender; required in group chats, omit in 1:1 chats (WhatsApp JID: individual as `<digits>@s.whatsapp.net` or bare phone digits, group as `<digits>-<timestamp>@g.us`)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changedv0.3.0
    • changedInput schema / properties / emoji / description
      Previous value: -"single emoji, or empty string to clear the reaction"New value: +"single emoji to react with; pass an empty string to clear an existing reaction"
    • changedInput schema / properties / message_id / description
      Previous value: -"WhatsApp message ID"New value: +"WhatsApp message ID of the target message (use `message_id` from list_messages)"
    • changedInput schema / properties / sender_jid / description
      Previous value: -"original sender; required in group chats (WhatsApp JID: individual as `<digits>@s.whatsapp.net` or bare phone digits, group as `<digits>-<timestamp>@g.us`)"New value: +"JID of the original sender; required in group chats, omit in 1:1 chats (WhatsApp JID: individual as `<digits>@s.whatsapp.net` or bare phone digits, group as `<digits>-<timestamp>@g.us`)"
  2. First observedv0.1.0

TDQS

A4.7/5.0
Behavior5/5

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

Discloses reversible behavior via empty emoji, return value of 'Reaction sent', and hints that it is idempotent (aligns with annotation). No contradiction with annotations.

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?

Three concise sentences; first sentence immediately states core purpose. No superfluous content.

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

Completeness5/5

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

For a 4-parameter tool with no output schema, the description covers all: purpose, usage guidance, return value, and parameter hints. Sibling tools are mentioned. Complete given the tool's complexity.

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 coverage is 100% and already describes all parameters thoroughly. Description adds no significant new semantics beyond restating the emoji empty string case.

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 'Add or replace an emoji reaction on an existing message' and distinguishes it from siblings by specifying 'for a fresh message use send_message and for a quoted reply use send_reply'.

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

Usage Guidelines5/5

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

Explicitly tells when to use (react to existing message) and when not (use send_message for fresh, send_reply for quoted reply), and explains reversibility with empty emoji.

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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