write_kv_value · Cloudflare MCP Server MCP: Risk & Policy

WHAT IT DOES

What write_kv_value does on Cloudflare MCP Server

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

WHY IT NEEDS A POLICY

Why write_kv_value needs a policy

This tool creates or modifies data reversibly in Workers KV storage without deleting or destroying existing records. While it could potentially overwrite existing values (which is a modification, not destruction), the action is reversible through subsequent writes or deletes.

From the tool's definition Tool name 'write_kv_value' and description states 'Write a key-value pair to Workers KV storage' — creates or modifies data in cloud storage.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_kv_value Rate-limited

write_kv_value 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": {
    "write_kv_value": {
      "limits": [
        {
          "counter": "write_kv_value_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 Cloudflare MCP Server, so you can run agents against it safely.

FAQ

Questions about write_kv_value

What does the write_kv_value tool do? +

Write a key-value pair to Workers KV storage. Can store text or metadata. It is categorised as a Write tool in the Cloudflare 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 write_kv_value? +

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

What risk level is write_kv_value? +

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

Can I rate-limit write_kv_value? +

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

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

write_kv_value is provided by the Cloudflare MCP Server MCP server (ry-ops/cloudflare-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.