web3_subscribe

THE RISK

Critical Risk

Why web3_subscribe needs a policy

This tool initiates a financial transaction by processing a USDC payment on the Base blockchain to subscribe to a paid tier. It directly moves cryptocurrency (USDC) and commits financial obligations, making it Financial category with critical severity due to the risk of unauthorized or erroneous payments.

From the tool's definition Subscribe to a paid tier (build or pro) using x402 USDC payment on Base

Documented attack patterns abuse exactly the kind of access web3_subscribe gives an agent:

POLICY

How to control web3_subscribe

PolicyLayer is an MCP gateway — it sits between your AI agents and 0xarchive, and nothing reaches the server without passing your rules. This is the rule we recommend for web3_subscribe:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "web3_subscribe": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}

Any call to web3_subscribe is blocked until a human approves it. The rest of the server keeps working.

Create a free account and register 0xarchive — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

GATE THIS TOOL →

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EXPLORE

Related tools and policies

More 0xarchive tools

Destructive web3_revoke_key Revoke a specific API key. Requires a fresh SIWE challenge signed with personal_sign. Write web3_signup Create a free-tier 0xArchive account and get an API key using a signed SIWE message. Read web3_challenge Get a SIWE (Sign-In with Ethereum) challenge message for a wallet address. Read web3_list_keys List all API keys for a wallet. Requires a fresh SIWE challenge signed with personal_sign.

All 5 0xarchive tools →

Financial tools on other servers

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Go deeper

Critical-risk tools in 0xarchive → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Human-in-the-loop → When a tool call should wait for a person — and when policy can decide alone.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
How to Add Spending Controls to Any MCP Agent →
Rate Limiting MCP Tool Calls: A Practical Guide →

FAQ

Questions about web3_subscribe

What does the web3_subscribe tool do? +

Subscribe to a paid tier (build or pro) using x402 USDC payment on Base.\n\n. It is categorised as a Financial tool in the 0xarchive MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on web3_subscribe? +

Register the 0xarchive MCP server in PolicyLayer and add a rule for web3_subscribe: 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 0xarchive. Nothing to install.

What risk level is web3_subscribe? +

web3_subscribe is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit web3_subscribe? +

Yes. Add a rate_limit block to the web3_subscribe 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 web3_subscribe completely? +

Set action: deny in the PolicyLayer policy for web3_subscribe. 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 web3_subscribe? +

web3_subscribe is provided by the 0xarchive MCP server (0xarchiveio/0xarchive-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every 0xarchive tool call.

Start from 0xarchive, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →