AI agents call download_file to retrieve information from Adb without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
While file downloading is a Read operation (data retrieval), the medium severity is justified because: (1) an AI agent could exfiltrate sensitive data from the Android device (credentials, private messages, health data, financial records), (2) base64 encoding facilitates data exfiltration by preparing it for transmission, and (3) the blast radius includes exposure of arbitrary files the Android user has access to.
From the tool's definition Tool downloads files from an Android device and converts to base64. The description states '下载设备上的文件并转换为base64' (download file on device and convert to base64). This is fundamentally a retrieval operation with no modification or deletion of device data.
Documented attack patterns abuse exactly the kind of access download_file gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Adb, and nothing reaches the server without passing your rules. This is the rule we recommend for download_file:
{
"version": "1",
"default": "deny",
"tools": {
"download_file": {}
}
}download_file is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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下载设备上的文件并转换为base64. It is categorised as a Read tool in the Adb MCP Server, which means it retrieves data without modifying state.
Register the Adb MCP server in PolicyLayer and add a rule for download_file: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Adb. Nothing to install.
download_file is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the download_file rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for download_file. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
download_file is provided by the Adb MCP server (wolfcoming/adb_mcp_server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Adb, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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48 Adb tools catalogued and risk-classified — across an index of 43,000+ MCP servers.