store_blob · Walrus MCP Server MCP: Risk & Policy

WHAT IT DOES

What store_blob does on Walrus MCP Server

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

WHY IT NEEDS A POLICY

Why store_blob needs a policy

This tool creates/writes new data (a blob) to a decentralized storage network. It is a reversible write operation since there is a sibling 'delete_blob' tool, indicating blobs can be removed after creation. No code execution, financial transaction, or irreversible destruction is implied.

From the tool's definition Store a blob in Walrus decentralized storage

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

store_blob Rate-limited

store_blob 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": {
    "store_blob": {
      "limits": [
        {
          "counter": "store_blob_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 Walrus MCP Server, so you can run agents against it safely.

FAQ

Questions about store_blob

What does the store_blob tool do? +

Store a blob in Walrus decentralized storage. It is categorised as a Write tool in the Walrus 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 store_blob? +

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

What risk level is store_blob? +

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

Can I rate-limit store_blob? +

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

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

store_blob is provided by the Walrus MCP Server MCP server (motion-labs-sui/walrus-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.