Validate an EU VAT number against VIES. Returns whether the number is a valid/registered EU VAT registration, plus the registered name and address when the member state publishes them (many states return "---" or empty even for valid numbers). A false result means not registered/invalid. If the n...
Part of the Vies Eu server.
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AI agents call check_vat to retrieve information from Vies Eu 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 check_vat 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": {
"check_vat": {}
}
}See the full Vies Eu policy for all 22 tools.
These attack patterns abuse exactly the kind of access check_vat 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.
Validate an EU VAT number against VIES. Returns whether the number is a valid/registered EU VAT registration, plus the registered name and address when the member state publishes them (many states return "---" or empty even for valid numbers). A false result means not registered/invalid. If the national service is temporarily down, userError is MS_UNAVAILABLE/MS_MAX_CONCURRENT_REQ etc. — treat that as "could not check", not "invalid".. It is categorised as a Read tool in the Vies Eu MCP Server, which means it retrieves data without modifying state.
Register the Vies Eu MCP server in PolicyLayer and add a rule for check_vat: 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 Vies Eu. Nothing to install.
check_vat 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 check_vat 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 check_vat. 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.
check_vat is provided by the Vies Eu MCP server (https://gateway.pipeworx.io/vies-eu/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 22 Vies Eu tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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