Update a configuration value in the voicemode.env file. Args: key: The configuration key to update (e.g., 'VOICEMODE_VOICES') value: The new value for the configuration Returns: Confirmation message with the updated configuration
AI agents use update_config to create or update resources in Voice Mode — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Voice Mode environment.
This tool creates or modifies data (configuration settings) in a reversible manner. While config changes can have significant side effects on system behavior (justifying 'high' severity—misconfiguration could disable critical audio features or alter security-relevant settings), the action itself is Write-category: updates are not irreversible deletions (Destructive), do not execute arbitrary code (Execute), and do…
From the tool's definition Tool description states it 'Update[s] a configuration value in the voicemode.env file' with arguments for key and value. This is a reversible modification of configuration data.
Documented attack patterns abuse exactly the kind of access update_config gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Voice Mode, and nothing reaches the server without passing your rules. This is the rule we recommend for update_config:
{
"version": "1",
"default": "deny",
"tools": {
"update_config": {
"limits": [
{
"counter": "update_config_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_config stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Update a configuration value in the voicemode.env file. Args: key: The configuration key to update (e.g., 'VOICEMODE_VOICES') value: The new value for the configuration Returns: Confirmation message with the updated configuration. It is categorised as a Write tool in the Voice Mode MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Voice Mode MCP server in PolicyLayer and add a rule for update_config: 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 Voice Mode. Nothing to install.
update_config is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the update_config 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 update_config. 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.
update_config is provided by the Voice Mode MCP server (mbailey/voicemode). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Voice Mode, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
25 Voice Mode tools catalogued and risk-classified — across an index of 43,000+ MCP servers.