Set or update an environment variable for your Rails application on Hatchbox. This tool uses the Hatchbox API to modify environment variables, which will be applied on the next deployment. Changes do not take effect immediately - you must trigger a deployment after setting variables. Example resp...
AI agents use setEnvVar to create or update resources in Playwright Stealth — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Playwright Stealth environment.
This tool creates or modifies environment variables in a Rails application via the Hatchbox API. While modifications are reversible (variables can be changed back), the blast radius is high because environment variables can contain API keys, credentials, feature flags, and configuration that directly affects application behavior.
From the tool's definition Tool description explicitly states 'Set or update an environment variable' and 'modify environment variables', indicating reversible creation/modification of configuration data. The example shows successful setting of a feature flag.
Documented attack patterns abuse exactly the kind of access setEnvVar gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Playwright Stealth, and nothing reaches the server without passing your rules. This is the rule we recommend for setEnvVar:
{
"version": "1",
"default": "deny",
"tools": {
"setEnvVar": {
"limits": [
{
"counter": "setenvvar_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}setEnvVar 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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Set or update an environment variable for your Rails application on Hatchbox. This tool uses the Hatchbox API to modify environment variables, which will be applied on the next deployment. Changes do not take effect immediately - you must trigger a deployment after setting variables. Example response: Successfully set environment variable: FEATURE_FLAG_ENABLED=true Use cases: - Enabling or disabling feature flags - Updating API endpoints or external service URLs - Changing application configuration values - Setting new API keys or credentials - Adjusting performance tuning parameters - Configuring third-party service integrations Important notes: - Changes require a deployment to take effect - Use getEnvVars to verify current values before changes - Requires READONLY=false in configuration - Some variables like RAILS_ENV should be changed with caution. It is categorised as a Write tool in the Playwright Stealth MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Playwright Stealth MCP server in PolicyLayer and add a rule for setEnvVar: 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 Playwright Stealth. Nothing to install.
setEnvVar 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 setEnvVar 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 setEnvVar. 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.
setEnvVar is provided by the Playwright Stealth MCP server (pulsemcp/mcp-servers). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Playwright Stealth, 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.
68 Playwright Stealth tools catalogued and risk-classified — across an index of 43,000+ MCP servers.