AI agents use block_domain to create or update resources in OPNSense MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your OPNSense MCP Server environment.
This tool creates a new DNS blocklist entry, which is a reversible write operation. While it affects network traffic by blocking a domain, the entry can be removed or modified. It is not destructive (no deletion), not execute (no arbitrary code execution), and not financial.
From the tool's definition Tool name 'block_domain' and description 'Add a domain to the DNS blocklist' indicate creation of a new blocklist entry. The verb 'Add' and the action of modifying firewall DNS filtering rules constitute data modification.
Documented attack patterns abuse exactly the kind of access block_domain gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and OPNSense MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for block_domain:
{
"version": "1",
"default": "deny",
"tools": {
"block_domain": {
"limits": [
{
"counter": "block_domain_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}block_domain 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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Add a domain to the DNS blocklist. It is categorised as a Write tool in the OPNSense MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the OPNSense MCP Server MCP server in PolicyLayer and add a rule for block_domain: 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 OPNSense MCP Server. Nothing to install.
block_domain 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 block_domain 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 block_domain. 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.
block_domain is provided by the OPNSense MCP Server MCP server (vespo92/opnsensemcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 196 OPNSense MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
196 OPNSense MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.