Authorize an account to hold a Multi-Purpose Token (MPT), or as a holder, opt-in to hold an MPT. For MPTs with requireAuth flag, issuers must authorize holders before they can receive tokens.
AI agents use mpt-authorize 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.
This tool creates or modifies authorization records on the XRP Ledger—a reversible write operation. While it affects financial token holdings, it does not move money or commit financial obligations itself; it only grants permissions. The action is Write rather than Execute because it is a specific ledger state modification rather than arbitrary code execution.
From the tool's definition 'Authorize an account to hold a Multi-Purpose Token (MPT)' and 'opt-in to hold an MPT' indicate this tool modifies account state by granting authorization permissions.
Documented attack patterns abuse exactly the kind of access mpt-authorize 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 mpt-authorize:
{
"version": "1",
"default": "deny",
"tools": {
"mpt-authorize": {
"limits": [
{
"counter": "mpt-authorize_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}mpt-authorize 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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Authorize an account to hold a Multi-Purpose Token (MPT), or as a holder, opt-in to hold an MPT. For MPTs with requireAuth flag, issuers must authorize holders before they can receive tokens. 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 mpt-authorize: 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.
mpt-authorize 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 mpt-authorize 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 mpt-authorize. 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.
mpt-authorize 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.
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