@aiwerk/mcp-server-elevenlabs

whatsapp_outbound_message

Send an outbound WhatsApp message using a template to reach a user and start an agent-driven conversation.

Instructions

Send An Outbound Message Via Whatsapp

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": {
      "whatsapp_phone_number_id": "<whatsapp_phone_number_id>",
      "whatsapp_user_id": "<whatsapp_user_id>",
      "template_name": "<template_name>",
      "template_language_code": "<template_language_code>",
      "template_params": "<template_params>",
      "agent_id": "<agent_id>"
    },
    "name": "whatsapp_outbound_message"
  }
}

Input Schema

Name	Required	Description	Default
`agent_id`	Yes
`template_name`	Yes
`template_params`	Yes
`whatsapp_user_id`	Yes
`template_language_code`	Yes
`whatsapp_phone_number_id`	Yes
`conversation_initiation_client_data`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 13, 2026

TDQS

C2.6/5.0

Behavior2/5

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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds nothing beyond that: it does not mention that WhatsApp outbound messages require pre-approved templates, that template_params must match the template, or any rate/auth constraints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence with zero fluff. It is efficient, though its brevity comes at the cost of substance rather than being a model of tight specification.

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 7-parameter, 6-required mutation tool with 0% schema coverage and no output schema, the description is far too thin. It should at minimum explain the template-based nature of WhatsApp messaging and what each required identifier refers to.

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

Parameters1/5

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

Schema description coverage is 0% across 7 parameters (6 required), and the description names none of them. An agent has no clue from the text that template_name, template_language_code, template_params, agent_id, or the phone/user IDs are needed, nor what format template_params takes.

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?

States a specific verb and resource ('Send An Outbound Message Via Whatsapp'), so an agent knows this initiates a WhatsApp message. It does not, however, distinguish itself from siblings like whatsapp_outbound_call or handle_twilio_outbound_call, leaving channel selection to inference.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives such as whatsapp_outbound_call for voice. An agent gets no help deciding between the outbound-message and outbound-call tools.

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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