Create a new user profile or merge supplied values into an existing profile (POST). Existing fields not included are preserved.
Part of the Courier server.
Free to start. No card required.
AI agents use create_or_merge_user to create or modify resources in Courier. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call create_or_merge_user repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Courier.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"create_or_merge_user": {
"limits": [
{
"counter": "create_or_merge_user_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Courier policy for all 123 tools.
These attack patterns abuse exactly the kind of access create_or_merge_user gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Create a new user profile or merge supplied values into an existing profile (POST). Existing fields not included are preserved.. It is categorised as a Write tool in the Courier MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Courier MCP server in PolicyLayer and add a rule for create_or_merge_user: 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 Courier. Nothing to install.
create_or_merge_user 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 create_or_merge_user 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 create_or_merge_user. 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.
create_or_merge_user is provided by the Courier MCP server (https://mcp.courier.com). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 123 Courier tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.