Verify that an incoming webhook callback came from PicPay by comparing the x-seller-token header against PICPAY_SELLER_TOKEN. Use this in your callback handler before trusting the payload, then call get_payment_status to fetch the authoritative status.
AI agents call validate_notification to retrieve information from Mcp Ap2 without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a security validation/authentication tool that checks webhook authenticity before processing. It reads and compares header values but does not perform any state-changing operations. The actual payment status is retrieved via a separate tool. The function is defensive and read-only in nature, similar to validating signatures or verifying certificates.
From the tool's definition Tool performs verification and comparison of authentication headers ('comparing the x-seller-token header against PICPAY_SELLER_TOKEN') and validation checks.
Documented attack patterns abuse exactly the kind of access validate_notification gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for validate_notification:
{
"version": "1",
"default": "deny",
"tools": {
"validate_notification": {}
}
}validate_notification is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Verify that an incoming webhook callback came from PicPay by comparing the x-seller-token header against PICPAY_SELLER_TOKEN. Use this in your callback handler before trusting the payload, then call get_payment_status to fetch the authoritative status. It is categorised as a Read tool in the Mcp Ap2 MCP Server, which means it retrieves data without modifying state.
Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for validate_notification: 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 Ap2. Nothing to install.
validate_notification 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 validate_notification 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 validate_notification. 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.
validate_notification is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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1300 Mcp Ap2 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.