write_config_file

Write content to a config file. Validates YAML syntax before saving (set validate_yaml=False to skip).

SERVERHa Nexus Agent SOURCEfistacho/ha-nexus-agent

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/fistacho-ha-nexus-agent/write-config-file.md

WHAT IT DOES

What write_config_file does on Ha Nexus Agent

AI agents use write_config_file to create or update resources in Ha Nexus Agent, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ha Nexus Agent environment.

RISK

Why write_config_file is rated Medium

This tool modifies configuration files, which is a reversible write operation. While not destructive by itself (old configs could theoretically be restored), it has high severity because writing to Home Assistant config files can cause system misconfigurations, disable automations, alter device control settings, or break integrations—affecting all connected smart home devices.

From the tool's definition Tool description states 'Write content to a config file' with YAML validation capability. The name 'write_config_file' explicitly indicates file writing operations.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs write_config_file safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Ha Nexus Agent, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For write_config_file, this is the rule to start with:

write_config_file Rate-limited

write_config_file 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "write_config_file": {
      "limits": [
        {
          "counter": "write_config_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Ha Nexus Agent, apply this rule, and every write_config_file call is checked against it from then on.

FAQ

Questions about write_config_file

What does the write_config_file tool do? +

Write content to a config file. Validates YAML syntax before saving (set validate_yaml=False to skip). It is categorised as a Write tool in the Ha Nexus Agent MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on write_config_file? +

Register the Ha Nexus Agent MCP server in PolicyLayer and add a rule for write_config_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 Ha Nexus Agent. Nothing to install.

What risk level is write_config_file? +

write_config_file is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit write_config_file? +

Yes. Add a rate_limit block to the write_config_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.

How do I block write_config_file completely? +

Set action: deny in the PolicyLayer policy for write_config_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.

What MCP server provides write_config_file? +

write_config_file is provided by the Ha Nexus Agent MCP server (fistacho/ha-nexus-agent). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

More on Ha Nexus Agent, and thousands of servers like it.

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All 276 Ha Nexus Agent tools →

Across the catalogue

team_manager_write_memory on Team Manager MCP → The MCP Attack Database →

Guides

Govern customer-ops agents →Argument validation →Scoped token →