Fetch the most recent Norges Bank (Norway's central bank, Norges Bank in Norwegian — the official issuer of the krone) exchange-rate reference between two currencies. Norges Bank publishes the daily NOK reference rate at ~16:00 Oslo time and Norwegian tax + accounting authorities (Skatteetaten / ...
Part of the Mcp server.
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AI agents call get_exchange_rate to retrieve information from Mcp 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 get_exchange_rate 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": {
"get_exchange_rate": {}
}
}See the full Mcp policy for all 13 tools.
These attack patterns abuse exactly the kind of access get_exchange_rate 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.
Fetch the most recent Norges Bank (Norway's central bank, Norges Bank in Norwegian — the official issuer of the krone) exchange-rate reference between two currencies. Norges Bank publishes the daily NOK reference rate at ~16:00 Oslo time and Norwegian tax + accounting authorities (Skatteetaten / Norwegian Tax Administration; Regnskapsloven / Accounting Act) accept it as the canonical conversion benchmark for obligations denominated in foreign currency — including annual accounts (Årsregnskap), MVA / VAT (Merverdiavgift) filings on cross-border transactions, and dividend reporting. Use this tool whenever an agent needs an authoritative NOK rate, OR a NOK-quoted rate against another currency, for a regulatory calculation. The response includes the rate value, the date the rate is valid for (Norges Bank publishes weekday rates only; weekends + Norwegian public holidays return the prior business day's rate), and the source attribution so the agent can cite it back to a user. This is one of the few tools that does NOT depend on Norwegian-company input; it is the currency-of-record lookup. Input: { base, quote } as ISO 4217 three-letter currency codes (uppercase, exactly 3 chars). Either side can be NOK or any other currency Norges Bank publishes. Failure modes the agent must handle: VALIDATION_FAILED on a non-ISO-4217 input; UPSTREAM_TIMEOUT if Norges Bank is slow; 404 not_found if the (base, quote) pair is not in the published set; SCOPE_INSUFFICIENT if the API key is not scoped read:norgesbank.. It is categorised as a Read tool in the Mcp MCP Server, which means it retrieves data without modifying state.
Register the MCP server in PolicyLayer and add a rule for get_exchange_rate: 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 Mcp. Nothing to install.
get_exchange_rate 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_exchange_rate 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_exchange_rate. 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_exchange_rate is provided by the MCP server (https://www.apier.no/api/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 13 Mcp tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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