Establish trust line to approve token usage
AI agents use approve-token-spending to create or update resources in Xrpl mcp — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Xrpl mcp environment.
Approving token spending establishes a trust line, which modifies account state on the ledger. This is a Write operation (creates/modifies data reversibly) rather than Execute because it does not run arbitrary code or trigger conditional external operations—it performs a well-defined ledger transaction. While it enables subsequent token transfers, the tool itself only sets permissions.
From the tool's definition Tool name 'approve-token-spending' and description 'Establish trust line to approve token usage' indicate creating or modifying a trust line on the XRP Ledger, which is a reversible ledger state change that enables token transfers.
Documented attack patterns abuse exactly the kind of access approve-token-spending gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Xrpl mcp, and nothing reaches the server without passing your rules. This is the rule we recommend for approve-token-spending:
{
"version": "1",
"default": "deny",
"tools": {
"approve-token-spending": {
"limits": [
{
"counter": "approve-token-spending_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}approve-token-spending stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Establish trust line to approve token usage. It is categorised as a Write tool in the Xrpl mcp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Xrpl MCP server in PolicyLayer and add a rule for approve-token-spending: 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 Xrpl mcp. Nothing to install.
approve-token-spending is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the approve-token-spending 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 approve-token-spending. 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.
approve-token-spending is provided by the Xrpl MCP server (romthpt/mcp-xrpl). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Xrpl mcp, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
71 Xrpl mcp tools catalogued and risk-classified — across an index of 43,000+ MCP servers.