cache_set · Awslabs Valkey MCP: Risk & Policy

WHAT IT DOES

What cache_set does on Awslabs Valkey

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

WHY IT NEEDS A POLICY

Why cache_set needs a policy

The tool creates or modifies cached data, which is reversible (values can be overwritten or deleted). This is a Write operation. Severity is medium because misuse could corrupt application cache state or inject malicious data into a shared cache store accessed by other applications, but the impact is generally limited to the cache layer and can be remediated by cache eviction or updates.

From the tool's definition Tool name is 'cache_set' and description states 'Set a value in the cache' — this is a create/modify operation that persists data to the cache store.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

cache_set Rate-limited

cache_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": {
    "cache_set": {
      "limits": [
        {
          "counter": "cache_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 Awslabs Valkey, so you can run agents against it safely.

FAQ

Questions about cache_set

What does the cache_set tool do? +

Set a value in the cache. It is categorised as a Write tool in the Awslabs Valkey MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on cache_set? +

Register the Awslabs Valkey MCP server in PolicyLayer and add a rule for cache_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 Awslabs Valkey. Nothing to install.

What risk level is cache_set? +

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

Can I rate-limit cache_set? +

Yes. Add a rate_limit block to the cache_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 cache_set completely? +

Set action: deny in the PolicyLayer policy for cache_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 cache_set? +

cache_set is provided by the Awslabs Valkey MCP server (awslabs.valkey-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.