concat_hex

THE RISK

Low Risk

Why concat_hex needs a policy

This tool performs a pure data transformation operation - concatenating hex strings. It has no side effects, does not read from any data source, does not execute code, and does not modify any state. It is a utility/helper function for string manipulation.

From the tool's definition Concatenate multiple hex strings together

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

POLICY

How to control concat_hex

PolicyLayer is an MCP gateway — it sits between your AI agents and Sperax Ecosystem Crypto & DeFI MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for concat_hex:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "concat_hex": {
      "limits": [
        {
          "counter": "concat_hex_rate",
          "window": "minute",
          "max": 60,
          "scope": "grant"
        }
      ]
    }
  }
}

concat_hex gets a rate cap, and everything else on the server is denied unless you say otherwise.

Create a free account and register Sperax Ecosystem Crypto & DeFI 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.

SET A RULE FOR THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Tool risk categories → How PolicyLayer classifies MCP tools by what they can do.
MCP tool → What an MCP tool is and how clients discover and call it.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about concat_hex

What does the concat_hex tool do? +

Concatenate multiple hex strings together. It is categorised as a Other tool in the Sperax Ecosystem Crypto & DeFI MCP Server MCP Server, which means it performs auxiliary operations.

How do I enforce a policy on concat_hex? +

Register the Sperax Ecosystem Crypto & DeFI MCP Server MCP server in PolicyLayer and add a rule for concat_hex: 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 Sperax Ecosystem Crypto & DeFI MCP Server. Nothing to install.

What risk level is concat_hex? +

concat_hex is a Other tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit concat_hex? +

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

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

concat_hex is provided by the Sperax Ecosystem Crypto & DeFI MCP Server MCP server (sperax/sperax-crypto-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Sperax Ecosystem Crypto & DeFI MCP Server tool call.

Start from Sperax Ecosystem Crypto & DeFI 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 →