Look up all currencies supported by the marketstack API.
AI agents call list_currencies to retrieve information from Marketstack MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a simple data retrieval operation—listing supported currencies—which is a read-only query with no capability to modify, delete, or execute code. The blast radius of misuse is minimal since it only exposes reference metadata. No financial transactions, data destruction, or code execution is involved.
From the tool's definition Tool name 'list_currencies' and description 'Look up all currencies supported by the marketstack API' indicates a query/lookup operation that retrieves static reference data without modification, deletion, or execution of side effects.
Attacks that exploit this kind of access
Look up all currencies supported by the marketstack API. It is categorised as a Read tool in the Marketstack MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Marketstack MCP Server MCP server in PolicyLayer and add a rule for list_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 Marketstack MCP Server. Nothing to install.
list_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 list_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 list_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.
list_currencies is provided by the Marketstack MCP Server MCP server (matteoantoci/mcp-marketstack). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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