switch_schema · Dm MCP: Risk & Policy

WHAT IT DOES

What switch_schema does on Dm

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

WHY IT NEEDS A POLICY

Why switch_schema needs a policy

This tool switches the active schema context for the database session. It modifies the session/connection state (which schema is currently active), which is a reversible write-like operation. It does not delete data, execute arbitrary code, or move money. The blast radius is medium because changing the active schema could cause subsequent queries or operations to affect unintended tables/data.

From the tool's definition 切换当前操作的SCHEMA（仅在配置了DAMENG_ALLOWED_SCHEMAS时可用）

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

switch_schema Rate-limited

switch_schema 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": {
    "switch_schema": {
      "limits": [
        {
          "counter": "switch_schema_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 Dm, so you can run agents against it safely.

FAQ

Questions about switch_schema

What does the switch_schema tool do? +

切换当前操作的SCHEMA（仅在配置了DAMENG_ALLOWED_SCHEMAS时可用）. It is categorised as a Write tool in the Dm MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on switch_schema? +

Register the Dm MCP server in PolicyLayer and add a rule for switch_schema: 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 Dm. Nothing to install.

What risk level is switch_schema? +

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

Can I rate-limit switch_schema? +

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

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

switch_schema is provided by the Dm MCP server (tgich/dm_mcp_server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.