wwebjs-mcp

message_downloadMedia

Download media files attached to a specific WhatsApp message. Provide the session, chat, and message IDs to retrieve the attachment.

Instructions

[Message] Download attached message media

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_downloadMedia"
  }
}

Input Schema

Name	Required	Description
`chatId`	No	The chat id which contains the message
`messageId`	No	Unique WhatsApp ID 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?

With no annotations, the description carries the full burden of disclosing behavior. It does not describe what happens when media is downloaded—whether it saves to disk, returns a buffer, or produces a URL—nor does it mention limitations or required authorization. The description essentially restates the tool name without adding behavioral context.

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?

The description is a single, direct sentence that immediately conveys the core action. It is free of unnecessary words and front-loaded with the key verb. However, it is so brief that it misses opportunities to include useful context, but for what it is, it is structurally efficient.

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?

This is a download tool with three parameters and no output schema or annotations. The description is far too minimal to be complete: it does not explain what the user will receive, whether chatId and messageId are both required for the download, or what media types are supported. Sibling tool message_downloadMediaAsData hints at a possible data-return variant, but no distinction is made.

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 description coverage, so the baseline is 3. The description adds no additional semantics beyond stating 'attached message media,' which does not meaningfully clarify how chatId, messageId, or sessionId are used in the download process.

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 'Download attached message media' clearly states the tool's action (download) and resource (attached message media). It is specific enough to understand the primary function, though it does not differentiate between this tool and the sibling message_downloadMediaAsData, leaving some ambiguity about the output format.

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 provided on when to use this tool versus alternatives. The existence of message_downloadMediaAsData suggests a potential alternative, but no distinction is made. There is also no mention of prerequisites or typical use cases.

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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