AI agents call find_cpf_by_mask to retrieve information from Cpf Validador without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
While this is a Read operation (no data modification), the severity is high because CPFs are sensitive personal identifiers in Brazil, and the ability to discover complete CPFs from partial masks poses privacy and identity fraud risks if misused by an AI agent.
From the tool's definition Tool name 'find_cpf_by_mask' combined with server description stating it 'discovers complete CPF from partial digits' indicates data retrieval.
Documented attack patterns abuse exactly the kind of access find_cpf_by_mask gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Cpf Validador, and nothing reaches the server without passing your rules. This is the rule we recommend for find_cpf_by_mask:
{
"version": "1",
"default": "deny",
"tools": {
"find_cpf_by_mask": {}
}
}find_cpf_by_mask is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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find_cpf_by_mask. It is categorised as a Read tool in the Cpf Validador MCP Server, which means it retrieves data without modifying state.
Register the Cpf Validador MCP server in PolicyLayer and add a rule for find_cpf_by_mask: 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 Cpf Validador. Nothing to install.
find_cpf_by_mask 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 find_cpf_by_mask 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 find_cpf_by_mask. 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.
find_cpf_by_mask is provided by the Cpf Validador MCP server (opastorello/cpf-validador). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Cpf Validador, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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6 Cpf Validador tools catalogued and risk-classified — across an index of 43,000+ MCP servers.