# write_config_file Write content to a config file. Validates YAML syntax before saving (set validate_yaml=False to skip). Agent View of the PolicyLayer registry record for `write_config_file`. HTML page: https://policylayer.com/tools/fistacho-ha-nexus-agent/write-config-file ## Facts - Tool: `write_config_file` - Server: Ha Nexus Agent (`fistacho/ha-nexus-agent`) — https://policylayer.com/tools/fistacho-ha-nexus-agent.md - Homepage: https://github.com/Fistacho/ha-nexus-agent - Risk category: Write (Medium risk) - Registry record: grade F, identity unverified - Server rate-limited: no - Parameters: 0 - Recommended policy verdict: Rate-limited ## Example call (MCP tools/call, JSON-RPC 2.0) ```json { "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "write_config_file", "arguments": {} } } ``` ## 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 own definition: "Tool description states 'Write content to a config file' with YAML validation capability. The name 'write_config_file' explicitly indicates file writing operations." ## Use case 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. ## Recommended policy (PolicyLayer) Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Ha Nexus Agent: ```json { "version": "1", "default": "deny", "tools": { "write_config_file": { "limits": [ { "counter": "write_config_file_rate", "window": "minute", "max": 30, "scope": "grant" } ] } } } ``` ## Other tools on Ha Nexus Agent (275) - `abort_config_flow` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/abort-config-flow.md - `abort_options_flow` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/abort-options-flow.md - `delete_area` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-area.md - `delete_automation` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-automation.md - `delete_backup` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-backup.md - `delete_blueprint` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-blueprint.md - `delete_card` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-card.md - `delete_category` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-category.md - `delete_config_file` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-config-file.md - `delete_css_custom_property` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-css-custom-property.md - `delete_event` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-event.md - `delete_label` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-label.md - `delete_media` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-media.md - `delete_pipeline` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-pipeline.md - `delete_script` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-script.md - `delete_style_preset` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-style-preset.md - `delete_theme` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-theme.md - `delete_zone` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/delete-zone.md - `git_rollback_file` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/git-rollback-file.md - `git_rollback_to_commit` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/git-rollback-to-commit.md - `notify_persistent_dismiss` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/notify-persistent-dismiss.md - `notify_persistent_dismiss_all` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/notify-persistent-dismiss-all.md - `remove_device` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/remove-device.md - `remove_energy_source` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/remove-energy-source.md - `remove_integration` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/remove-integration.md - `remove_item` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/remove-item.md - `restore_backup` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/restore-backup.md - `stop_ha` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/stop-ha.md - `uninstall_addon` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/uninstall-addon.md - `uninstall_hacs_repository` — Destructive — https://policylayer.com/tools/fistacho-ha-nexus-agent/uninstall-hacs-repository.md - …and 245 more: https://policylayer.com/tools/fistacho-ha-nexus-agent.md ## For agents This record is a snapshot. Live verdicts and the full registry: - Check every server in your MCP config at once: `npx -y policylayer stack` - Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md) - Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events` --- Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=fistacho-ha-nexus-agent · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/fistacho-ha-nexus-agent