WhatsApp MCP Server

send_audio_message

Send audio messages via WhatsApp Business API by providing recipient phone number and audio file URL. Use this tool to deliver voice messages through WhatsApp's business communication platform.

Instructions

Send an audio/voice message via WhatsApp Business API

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": {
      "to": "<to>",
      "audio_url": "<audio_url>"
    },
    "name": "send_audio_message"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	Recipient phone number with country code
`audio_url`	Yes	Public URL of the audio file to send
`phone_number_id`	No	WhatsApp Business phone number ID (optional, uses env var if not provided)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jan 12, 2026

TDQS

C2.9/5.0

Behavior2/5

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

With no annotations provided, the description carries full burden for behavioral disclosure but only states what the tool does at a high level. It doesn't mention important behavioral aspects like whether this is a synchronous or asynchronous operation, error handling, rate limits, authentication requirements, or what happens if the audio URL is inaccessible. The description is insufficient for a mutation tool with zero annotation coverage.

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, efficient sentence that directly states the tool's purpose without unnecessary words. It's appropriately sized and front-loaded with the core functionality, making it easy to parse quickly.

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 (sending messages) with no annotations and no output schema, the description is incomplete. It doesn't address what the tool returns, error conditions, success indicators, or how it fits within the broader WhatsApp Business API context. Given the complexity of messaging APIs and lack of structured metadata, more contextual information would be helpful.

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 schema already documents all three parameters thoroughly. The description doesn't add any additional meaning about parameters beyond what's in the schema (e.g., it doesn't explain format requirements for audio_url or provide examples). This meets the baseline expectation when schema coverage is complete.

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 clearly states the action ('send') and resource ('audio/voice message via WhatsApp Business API'), making the tool's purpose immediately understandable. However, it doesn't explicitly differentiate this tool from sibling tools like send_document_message or send_video_message, which would require mentioning it's specifically for audio files rather than other media types.

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?

The description provides no guidance on when to use this tool versus alternatives like send_text_message or send_video_message. There's no mention of prerequisites (such as needing a WhatsApp Business account), use cases for audio messages, or limitations compared to other messaging tools in the sibling list.

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

Deploy Server