vex_set · Git Steer MCP: Risk & Policy

WHAT IT DOES

What vex_set does on Git Steer

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

WHY IT NEEDS A POLICY

Why vex_set needs a policy

This tool modifies vulnerability metadata by writing OpenVEX status records (not_affected or affected) to a persistent state repository. While not destructive (the operation is reversible and does not delete data), and not financial, it is a write operation that creates or modifies vulnerability tracking records.

From the tool's definition Set OpenVEX status on a CVE finding (ADR-004). Persisted to the git-steer-state _vex store.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

vex_set Rate-limited

vex_set 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": {
    "vex_set": {
      "limits": [
        {
          "counter": "vex_set_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 Git Steer, so you can run agents against it safely.

FAQ

Questions about vex_set

What does the vex_set tool do? +

Set OpenVEX status on a CVE finding (ADR-004). Persisted to the git-steer-state _vex store. not_affected requires a justification; affected requires an actionStatement. It is categorised as a Write tool in the Git Steer MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on vex_set? +

Register the Git Steer MCP server in PolicyLayer and add a rule for vex_set: 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 Git Steer. Nothing to install.

What risk level is vex_set? +

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

Can I rate-limit vex_set? +

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

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

vex_set is provided by the Git Steer MCP server (ry-ops/git-steer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.