apply_schema_diff · Directus MCP Server MCP: Risk & Policy

WHAT IT DOES

What apply_schema_diff does on Directus MCP Server

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

WHY IT NEEDS A POLICY

Why apply_schema_diff needs a policy

Schema updates are reversible writes that modify the database structure but not data deletion or financial operations. However, schema changes can have significant blast radius—they can break applications, cause downtime, or corrupt data structures if misapplied. This justifies 'high' severity rather than 'medium' for a Write operation.

From the tool's definition Tool name 'apply_schema_diff' and description 'Update the instance' indicate modification of database schema. The server description confirms this tool enables 'schema manipulation' as part of comprehensive Directus instance management.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_schema_diff Rate-limited

apply_schema_diff 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": {
    "apply_schema_diff": {
      "limits": [
        {
          "counter": "apply_schema_diff_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 Directus MCP Server, so you can run agents against it safely.

FAQ

Questions about apply_schema_diff

What does the apply_schema_diff tool do? +

Update the instance\. It is categorised as a Write tool in the Directus MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on apply_schema_diff? +

Register the Directus MCP Server MCP server in PolicyLayer and add a rule for apply_schema_diff: 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 Directus MCP Server. Nothing to install.

What risk level is apply_schema_diff? +

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

Can I rate-limit apply_schema_diff? +

Yes. Add a rate_limit block to the apply_schema_diff 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 apply_schema_diff completely? +

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

apply_schema_diff is provided by the Directus MCP Server MCP server (skeyelab/directus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.