Convert an amount between two currencies using official ČNB rates. E.g., convert 100 EUR to CZK, or 50 USD to GBP (goes via CZK cross-rate). Optional date for historical conversion.
Part of the Cnb server.
Free to start. No card required.
AI agents use convert to create or modify resources in Cnb. 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 Cnb.
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 Cnb 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 between two currencies using official ČNB rates. E.g., convert 100 EUR to CZK, or 50 USD to GBP (goes via CZK cross-rate). Optional date for historical conversion.. It is categorised as a Write tool in the Cnb MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Cnb 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 Cnb. 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 Cnb MCP server (@czagents/cnb). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 3 Cnb 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.