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OPNsense MCP Server

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opn_add_firewall_rule

Control network traffic by creating an OPNsense firewall rule. Specify action, direction, interface, and addresses to pass, block, or reject connections.

Instructions

Create a new MVC firewall filter rule with savepoint protection where supported.

Use this when you need to add a firewall rule.

Savepoint protection applies on OPNsense < 26.7 only: there changes auto-revert in 60 seconds unless confirmed with opn_confirm_changes. OPNsense 26.7 removed the savepoint API upstream, so on 26.7+ changes apply immediately and are NOT rolled back automatically. Check opn_mcp_info first: if 'savepoint_support' is false, take a config backup with opn_download_config before changing rules that could lock you out.

IMPORTANT: This creates MVC rules (Settings > Firewall > Automation), not legacy GUI rules.

Parameters:

  • action: 'pass', 'block', or 'reject'

  • direction: 'in' or 'out'

  • interface: interface name (e.g. 'lan', 'wan', 'opt1')

  • ip_protocol: 'inet' (IPv4), 'inet6' (IPv6), or 'inet46' (dual-stack)

  • protocol: 'any', 'TCP', 'UDP', 'TCP/UDP', 'ICMP', etc.

  • source_net: source address/network or 'any'

  • source_not: invert source match (True = NOT source_net)

  • source_port: source port number or range, or empty for any

  • destination_net: destination address/network or 'any'

  • destination_not: invert destination match (True = NOT destination_net, e.g. !Private_Networks)

  • destination_port: port number or range (e.g. '80', '1000-2000'), or empty for any

  • gateway: force traffic via specific gateway (e.g. 'WAN_GW') for policy routing, or empty for default

  • log: enable logging for this rule (default: off)

  • quick: first-match wins (default: True). Set False for last-match-wins logic

  • sequence: rule ordering within priority group (default: 1, higher = later)

  • categories: comma-separated category UUIDs to assign to this rule

  • description: human-readable rule description

Returns: dict with 'revision' (str), 'uuid' (str), and 'result' (str).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
logNo
quickNo
actionNopass
gatewayNo
protocolNoany
sequenceNo
directionNoin
interfaceNolan
categoriesNo
source_netNoany
source_notNo
descriptionNo
ip_protocolNoinet
source_portNo
destination_netNoany
destination_notNo
destination_portNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Tool Definition Quality

A4.7/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations exist, so the description must carry behavioral info. It explains savepoint auto-revert behavior (60 seconds, version-dependent), the need to confirm changes via opn_confirm_changes, and the distinction from legacy rules. This is exactly what an agent needs.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Well-structured with a summary then parameter list Baby steps, but it's long. However every sentence adds value (savepoint, version behavior, param details). Could be slightly trimmed but not bloated.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 17 params and version-dependent behavior, the description covers savepoint semantics, version differences, backup guidance, and every parameter's meaning. No gaps.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema has 0% coverage; the description's parameter list gives meaning to all 17 params including defaults and inversion semantics (source_not: invert match). Each param has a brief but clear explanation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool 'Create[s] a new MVC firewall filter rule' with a specific verb and resource. It also distinguishes from other firewall tools by noting it's for MVC rules, not legacy GUI rules, and references related tools in the sibling list.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description says 'Use this when you need to add a firewall rule' and warns to check opn_mcp_info for savepoint support. However it doesn't explicitly state when NOT to use it (e.g., for legacy rules), though the MVC emphasis essentially implies that. No explicit alternatives mentioned beyond savepoint.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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