AI agents use PutV1InstancesMembersByUserId to create or update resources in BlindPay MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your BlindPay MCP Server environment.
This tool modifies user roles and permissions within a financial payment system (BlindPay stablecoin infrastructure). While it is reversible (Write category, not Destructive), the blast radius is high because unauthorized role changes could grant malicious actors administrative or financial access to payment operations, receivers, and blockchain wallets.
From the tool's definition Tool name 'PutV1InstancesMembersByUserId' uses HTTP PUT method for updates; description states 'Update Instance Member Role', indicating modification of user access permissions within a payment infrastructure system.
Documented attack patterns abuse exactly the kind of access PutV1InstancesMembersByUserId gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and BlindPay MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for PutV1InstancesMembersByUserId:
{
"version": "1",
"default": "deny",
"tools": {
"PutV1InstancesMembersByUserId": {
"limits": [
{
"counter": "putv1instancesmembersbyuserid_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}PutV1InstancesMembersByUserId 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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Update Instance Member Role. It is categorised as a Write tool in the BlindPay MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the BlindPay MCP Server MCP server in PolicyLayer and add a rule for PutV1InstancesMembersByUserId: 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 BlindPay MCP Server. Nothing to install.
PutV1InstancesMembersByUserId 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 PutV1InstancesMembersByUserId 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 PutV1InstancesMembersByUserId. 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.
PutV1InstancesMembersByUserId is provided by the BlindPay MCP Server MCP server (blindpaylabs/blindpay-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from BlindPay MCP Server, 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.
81 BlindPay MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.