search_by_tag

THE RISK

Low Risk

Why search_by_tag needs a policy

This tool performs a search query to locate and retrieve data (equipment/instruments/nodes) matching a tag pattern. It is a read-only operation that returns matching results without creating, modifying, deleting, or executing any side effects. The description indicates it is also deprecated, further reducing concern.

From the tool's definition Tool name 'search_by_tag' and description explicitly state it searches for equipment, instruments, or nodes by tag pattern—a retrieval operation with no modification capability.

Documented attack patterns abuse exactly the kind of access search_by_tag gives an agent:

POLICY

How to control search_by_tag

PolicyLayer is an MCP gateway — it sits between your AI agents and Engineering MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for search_by_tag:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "search_by_tag": {}
  }
}

search_by_tag is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Engineering MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about search_by_tag

What does the search_by_tag tool do? +

[DEPRECATED] Search for equipment, instruments, or nodes by tag pattern. Use search_execute(query_type=. It is categorised as a Read tool in the Engineering MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on search_by_tag? +

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

What risk level is search_by_tag? +

search_by_tag is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit search_by_tag? +

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

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

search_by_tag is provided by the Engineering MCP Server MCP server (puran-water/dexpi-sfiles-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Engineering MCP Server tool call.

Start from Engineering MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →