# fs_write

A write tool on the Container-MCP MCP server.

Agent View of the PolicyLayer registry record for `fs_write`. HTML page: https://policylayer.com/tools/54rt1n-container-mcp/fs-write

## Facts

- Tool: `fs_write`
- Server: Container-MCP (`54rt1n/container-mcp`) — https://policylayer.com/tools/54rt1n-container-mcp.md
- Homepage: https://github.com/54rt1n/container-mcp
- 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": "fs_write",
    "arguments": {}
  }
}
```

## Why fs_write is rated Medium

fs_write creates or modifies files in the sandboxed environment. While it cannot permanently damage the host system due to the containerized nature, it can reversibly modify data within the sandbox, making it a Write operation rather than Execute (which would run code) or Destructive (which would irreversibly delete).

From the tool's own definition: "Tool name 'fs_write' and server description indicating it provides sandboxed file system operations. The name explicitly indicates writing/creating file content."

## Use case

AI agents use fs_write to create or update resources in Container-MCP, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Container-MCP environment.

## Recommended policy (PolicyLayer)

Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Container-MCP:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "fs_write": {
      "limits": [
        {
          "counter": "fs_write_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}
```

## Other tools on Container-MCP (26)

- `fs_delete` — Destructive — https://policylayer.com/tools/54rt1n-container-mcp/fs-delete.md
- `list_delete` — Destructive — https://policylayer.com/tools/54rt1n-container-mcp/list-delete.md
- `system_run_command` — Execute — https://policylayer.com/tools/54rt1n-container-mcp/system-run-command.md
- `system_run_python` — Execute — https://policylayer.com/tools/54rt1n-container-mcp/system-run-python.md
- `web_browse` — Execute — https://policylayer.com/tools/54rt1n-container-mcp/web-browse.md
- `fs_list` — Read — https://policylayer.com/tools/54rt1n-container-mcp/fs-list.md
- `fs_read` — Read — https://policylayer.com/tools/54rt1n-container-mcp/fs-read.md
- `health_check` — Read — https://policylayer.com/tools/54rt1n-container-mcp/health-check.md
- `kb_read` — Read — https://policylayer.com/tools/54rt1n-container-mcp/kb-read.md
- `kb_search` — Read — https://policylayer.com/tools/54rt1n-container-mcp/kb-search.md
- `list_get` — Read — https://policylayer.com/tools/54rt1n-container-mcp/list-get.md
- `list_search` — Read — https://policylayer.com/tools/54rt1n-container-mcp/list-search.md
- `market_query` — Read — https://policylayer.com/tools/54rt1n-container-mcp/market-query.md
- `rss_fetch` — Read — https://policylayer.com/tools/54rt1n-container-mcp/rss-fetch.md
- `system_env_var` — Read — https://policylayer.com/tools/54rt1n-container-mcp/system-env-var.md
- `web_scrape` — Read — https://policylayer.com/tools/54rt1n-container-mcp/web-scrape.md
- `web_search` — Read — https://policylayer.com/tools/54rt1n-container-mcp/web-search.md
- `fs_apply_diff` — Write — https://policylayer.com/tools/54rt1n-container-mcp/fs-apply-diff.md
- `fs_move` — Write — https://policylayer.com/tools/54rt1n-container-mcp/fs-move.md
- `kb_create_document` — Write — https://policylayer.com/tools/54rt1n-container-mcp/kb-create-document.md
- `kb_manage` — Write — https://policylayer.com/tools/54rt1n-container-mcp/kb-manage.md
- `kb_update_triples` — Write — https://policylayer.com/tools/54rt1n-container-mcp/kb-update-triples.md
- `kb_write_content` — Write — https://policylayer.com/tools/54rt1n-container-mcp/kb-write-content.md
- `list_create` — Write — https://policylayer.com/tools/54rt1n-container-mcp/list-create.md
- `list_modify` — Write — https://policylayer.com/tools/54rt1n-container-mcp/list-modify.md
- `list_update` — Write — https://policylayer.com/tools/54rt1n-container-mcp/list-update.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=54rt1n-container-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/54rt1n-container-mcp