Convert an amount from one currency to another. Returns {amount, currency} rounded to the target's minor units. Upstream rounds rates per direction; for low-value sources, flip via get_rates for more precision.
Part of the Frankfurter server.
Free to start. No card required.
AI agents use convert to create or modify resources in Frankfurter. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call convert repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Frankfurter.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"convert": {
"limits": [
{
"counter": "convert_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Frankfurter policy for all 3 tools.
These attack patterns abuse exactly the kind of access convert gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Convert an amount from one currency to another. Returns {amount, currency} rounded to the target's minor units. Upstream rounds rates per direction; for low-value sources, flip via get_rates for more precision.. It is categorised as a Write tool in the Frankfurter MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Frankfurter MCP server in PolicyLayer and add a rule for convert: 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 Frankfurter. Nothing to install.
convert is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the convert 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 convert. 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.
convert is provided by the Frankfurter MCP server (https://mcp.frankfurter.dev/). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 3 Frankfurter tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.