Official NBU exchange rates for ALL currencies on a single day (the rate the National Bank of Ukraine sets daily). Returns one record per currency: {r030 (numeric currency code), txt (Ukrainian name), rate (UAH per 1 unit of the currency), cc (ISO-4217 code, e.g. USD/EUR/PLN), exchangedate (DD.MM...
Part of the Nbu Ua server.
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AI agents call exchange_rates to retrieve information from Nbu Ua without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though exchange_rates only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"exchange_rates": {}
}
}See the full Nbu Ua policy for all 25 tools.
These attack patterns abuse exactly the kind of access exchange_rates gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Official NBU exchange rates for ALL currencies on a single day (the rate the National Bank of Ukraine sets daily). Returns one record per currency: {r030 (numeric currency code), txt (Ukrainian name), rate (UAH per 1 unit of the currency), cc (ISO-4217 code, e.g. USD/EUR/PLN), exchangedate (DD.MM.YYYY)}. Omit date for today's rates.. It is categorised as a Read tool in the Nbu Ua MCP Server, which means it retrieves data without modifying state.
Register the Nbu Ua MCP server in PolicyLayer and add a rule for exchange_rates: 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 Nbu Ua. Nothing to install.
exchange_rates 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 exchange_rates 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 exchange_rates. 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.
exchange_rates is provided by the Nbu Ua MCP server (https://gateway.pipeworx.io/nbu-ua/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 25 Nbu Ua tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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