kv_set · AgentOS MCP: Risk & Policy

WHAT IT DOES

What kv_set does on AgentOS

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

WHY IT NEEDS A POLICY

Why kv_set needs a policy

The tool stores data in persistent key-value memory, which is a create/modify operation. It is reversible (data can be deleted via kv_delete or overwritten), so it falls under Write rather than Destructive. Severity is medium because misuse could corrupt agent state or memory, affecting workflow integrity, but the impact is limited to application state rather than system-wide or financial consequences.

From the tool's definition Tool name 'kv_set' and description 'Store a key-value pair' indicate data creation/modification in persistent memory. This is a write operation that creates or modifies data reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

kv_set Rate-limited

kv_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": {
    "kv_set": {
      "limits": [
        {
          "counter": "kv_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 AgentOS, so you can run agents against it safely.

FAQ

Questions about kv_set

What does the kv_set tool do? +

Store a key-value pair in persistent local memory with optional TTL and namespace. It is categorised as a Write tool in the AgentOS MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on kv_set? +

Register the AgentOS MCP server in PolicyLayer and add a rule for kv_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 AgentOS. Nothing to install.

What risk level is kv_set? +

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

Can I rate-limit kv_set? +

Yes. Add a rate_limit block to the kv_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 kv_set completely? +

Set action: deny in the PolicyLayer policy for kv_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 kv_set? +

kv_set is provided by the AgentOS MCP server (netflypsb/agentos). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.