Register an environment variable in the truthpack. Use this BEFORE using a new env var to prevent ghost-env errors.
Part of the Vibecheck server.
Free to start. No card required.
AI agents use register_env_var to create or modify resources in Vibecheck. 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 register_env_var 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 Vibecheck.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"register_env_var": {
"limits": [
{
"counter": "register_env_var_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Vibecheck policy for all 103 tools.
These attack patterns abuse exactly the kind of access register_env_var 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.
Register an environment variable in the truthpack. Use this BEFORE using a new env var to prevent ghost-env errors.. It is categorised as a Write tool in the Vibecheck MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Vibecheck MCP server in PolicyLayer and add a rule for register_env_var: 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 Vibecheck. Nothing to install.
register_env_var 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 register_env_var 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 register_env_var. 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.
register_env_var is provided by the Vibecheck MCP server (@vibecheckdev/vibecheck-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 103 Vibecheck 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.