wallet_createHmac

THE RISK

High Risk

Why wallet_createHmac needs a policy

This tool performs a cryptographic operation (HMAC generation) using private wallet keys. It is an execution of a cryptographic function rather than a simple read or write — it actively uses sensitive wallet key material to produce an authentication code. While it doesn't move funds or delete data, misuse could expose or misuse wallet keys in unintended ways.

From the tool's definition Creates an HMAC using wallet keys

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

POLICY

How to control wallet_createHmac

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "wallet_createHmac": {
      "limits": [
        {
          "counter": "wallet_createhmac_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

wallet_createHmac stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

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

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Bitcoin SV MCP Server tools

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All 80 Bitcoin SV MCP Server tools →

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Go deeper

Govern code and CI agents → Branch allowlists, approval on merges, and rate caps on the build and pipeline tools agents trigger.
High-risk tools in Bitcoin SV MCP Server → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-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.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about wallet_createHmac

What does the wallet_createHmac tool do? +

Creates an HMAC using wallet keys. It is categorised as a Execute tool in the Bitcoin SV MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on wallet_createHmac? +

Register the Bitcoin SV MCP Server MCP server in PolicyLayer and add a rule for wallet_createHmac: 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 Bitcoin SV MCP Server. Nothing to install.

What risk level is wallet_createHmac? +

wallet_createHmac is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit wallet_createHmac? +

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

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

wallet_createHmac is provided by the Bitcoin SV MCP Server MCP server (b-open-io/bsv-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Bitcoin SV MCP Server tool call.

Start from Bitcoin SV MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →