Call a CrossFin paid API endpoint with automatic x402 USDC payment on Base.
Part of the CrossFin server.
Free to start. No card required.
AI agents call call_paid_service to retrieve information from CrossFin 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 call_paid_service 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": {
"call_paid_service": {}
}
}See the full CrossFin policy for all 16 tools.
These attack patterns abuse exactly the kind of access call_paid_service 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.
Call a CrossFin paid API endpoint with automatic x402 USDC payment on Base.. It is categorised as a Read tool in the CrossFin MCP Server, which means it retrieves data without modifying state.
Register the CrossFin MCP server in PolicyLayer and add a rule for call_paid_service: 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 CrossFin. Nothing to install.
call_paid_service 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 call_paid_service 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 call_paid_service. 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.
call_paid_service is provided by the CrossFin MCP server (bubilife1202/crossfin). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 16 CrossFin tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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