AI agents call get_currencies to retrieve information from Web3 without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves metadata about supported currencies in the blockchain context. It is a read-only query with no capability to modify data, execute code, delete resources, or move funds. The blast radius of misuse is minimal—an AI agent could only retrieve information that is already publicly available. This aligns with the 'Read' category for data retrieval operations.
From the tool's definition Tool name 'get_currencies' and description 'Get available currencies' indicate a retrieval operation that queries static or reference data about available currencies without modifying, executing operations, or having destructive side effects.
Documented attack patterns abuse exactly the kind of access get_currencies gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Web3, and nothing reaches the server without passing your rules. This is the rule we recommend for get_currencies:
{
"version": "1",
"default": "deny",
"tools": {
"get_currencies": {}
}
}get_currencies is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get available currencies. It is categorised as a Read tool in the Web3 MCP Server, which means it retrieves data without modifying state.
Register the Web3 MCP server in PolicyLayer and add a rule for get_currencies: 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 Web3. Nothing to install.
get_currencies 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 get_currencies 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 get_currencies. 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.
get_currencies is provided by the Web3 MCP server (tumf/web3-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Web3, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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17 Web3 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.