AI agents call des_decrypt to retrieve information from Crypto_MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Decryption is a read operation that transforms ciphertext into plaintext. It does not create, modify, or delete data—it only reveals already-encrypted information. While the operation itself is cryptographic, the functional impact is equivalent to a retrieval/read operation. No destructive, financial, or code execution risk is present.
From the tool's definition Tool performs decryption ('decrypt text with des') which retrieves plaintext from ciphertext with no modification to stored data and no side effects.
Documented attack patterns abuse exactly the kind of access des_decrypt gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Crypto_MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for des_decrypt:
{
"version": "1",
"default": "deny",
"tools": {
"des_decrypt": {}
}
}des_decrypt is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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decrypt text with des. It is categorised as a Read tool in the Crypto_MCP MCP Server, which means it retrieves data without modifying state.
Register the Crypto_ MCP server in PolicyLayer and add a rule for des_decrypt: 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 Crypto_MCP. Nothing to install.
des_decrypt is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the des_decrypt 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.
Set action: deny in the PolicyLayer policy for des_decrypt. 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.
des_decrypt is provided by the Crypto_ MCP server (1595901624/crypto-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Crypto_MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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14 Crypto_MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.