AI agents call get_prepost 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 tool retrieves pre-posting order information by ID, which is a read-only operation with no side effects. However, given the financial payment protocol context (AP2 — Google's Agent-to-Agent Payment Protocol), accessing order or payment-related data has medium severity due to potential exposure of sensitive financial information, even though no actual financial transaction occurs.
From the tool's definition Tool name 'get_prepost' with description 'Get a pre-posting order by ID' indicates a retrieval operation that queries order data without modification.
Documented attack patterns abuse exactly the kind of access get_prepost 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 get_prepost:
{
"version": "1",
"default": "deny",
"tools": {
"get_prepost": {}
}
} get_prepost is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get a pre-posting order by ID. 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 get_prepost: 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.
get_prepost 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 get_prepost 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 get_prepost. 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.
get_prepost 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.