sfiles_add_stream

THE RISK

Medium Risk

Why sfiles_add_stream needs a policy

This tool creates new data structures (process streams) within engineering diagrams. While it modifies the diagram, the changes are reversible (streams can be removed or edited). The impact is limited to the diagram artifact itself with no destructive, financial, or code-execution implications.

From the tool's definition The tool name 'sfiles_add_stream' and description 'Add a stream connecting two units' indicate a create/modify operation.

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

POLICY

How to control sfiles_add_stream

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 sfiles_add_stream:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sfiles_add_stream": {
      "limits": [
        {
          "counter": "sfiles_add_stream_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

sfiles_add_stream 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.

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.

LIMIT THIS TOOL →

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EXPLORE

Related tools and policies

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about sfiles_add_stream

What does the sfiles_add_stream tool do? +

[Available via model_tx_apply or direct call] Add a stream connecting two units. See docs/FEATURE_PARITY_MATRIX.md for migration guide. It is categorised as a Write tool in the Engineering 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 sfiles_add_stream? +

Register the Engineering MCP Server MCP server in PolicyLayer and add a rule for sfiles_add_stream: 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 sfiles_add_stream? +

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

Can I rate-limit sfiles_add_stream? +

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

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

sfiles_add_stream 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 →