write_json_values · JSON Editor MCP: Risk & Policy

WHAT IT DOES

What write_json_values does on JSON Editor MCP

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

WHY IT NEEDS A POLICY

Why write_json_values needs a policy

This tool creates or modifies JSON data in files reversibly. It does not delete data (which would be Destructive), execute code or shell commands (which would be Execute), or move money (which would be Financial).

From the tool's definition Tool description explicitly states 'Write a value to a JSON file at a specified path' and 'Creates missing paths automatically.' Server description also confirms this tool enables 'write...operations.'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_json_values Rate-limited

write_json_values 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_json_values": {
      "limits": [
        {
          "counter": "write_json_values_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches JSON Editor MCP, so you can run agents against it safely.

FAQ

Questions about write_json_values

What does the write_json_values tool do? +

Write a value to a JSON file at a specified path using dot notation. Creates missing paths automatically. It is categorised as a Write tool in the JSON Editor MCP 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_json_values? +

Register the JSON Editor MCP server in PolicyLayer and add a rule for write_json_values: 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 JSON Editor MCP. Nothing to install.

What risk level is write_json_values? +

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

Can I rate-limit write_json_values? +

Yes. Add a rate_limit block to the write_json_values 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_json_values completely? +

Set action: deny in the PolicyLayer policy for write_json_values. 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_json_values? +

write_json_values is provided by the JSON Editor MCP server (peternagy1332/json-editor-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.