add-json · Things App MCP: Risk & Policy

WHAT IT DOES

What add-json does on Things App MCP

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

WHY IT NEEDS A POLICY

Why add-json needs a policy

The add-json tool creates new projects and to-dos in the Things 3 application. This is reversible (items can be deleted) and has no direct financial impact or code execution risk beyond the application's intended functionality. It falls squarely in the Write category.

From the tool's definition Tool description states: 'Create complex projects and to-dos' — this is a creation operation. The tool uses 'the Things JSON command' to construct data structures, indicating it modifies application state by adding new items.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add-json Rate-limited

add-json 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": {
    "add-json": {
      "limits": [
        {
          "counter": "add-json_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 Things App MCP, so you can run agents against it safely.

FAQ

Questions about add-json

What does the add-json tool do? +

Create complex projects and to-dos using the Things JSON command. Supports nested projects with headings, checklist items, and to-dos. The data should be an array of objects with. It is categorised as a Write tool in the Things App 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 add-json? +

Register the Things App MCP server in PolicyLayer and add a rule for add-json: 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 Things App MCP. Nothing to install.

What risk level is add-json? +

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

Can I rate-limit add-json? +

Yes. Add a rate_limit block to the add-json 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 add-json completely? +

Set action: deny in the PolicyLayer policy for add-json. 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 add-json? +

add-json is provided by the Things App MCP server (lucas-flatwhite/things-app-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.