Vultr MCP

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firewall_create_rule

Create a firewall rule within a Vultr firewall group, defining protocol, IP type, subnet, and optional ports or notes to control traffic access.

Instructions

Create a new firewall rule.

Args: firewall_group_id: The firewall group ID or description (e.g., "web-servers" or UUID) ip_type: IP type (v4 or v6) protocol: Protocol (tcp, udp, icmp, gre) subnet: IP subnet (use "0.0.0.0" for any IPv4, "::" for any IPv6) subnet_size: Subnet size (0-32 for IPv4, 0-128 for IPv6) ctx: FastMCP context for resource change notifications port: Port or port range (e.g., "80" or "8000:8999") - required for tcp/udp source: Source type (e.g., "cloudflare") - optional notes: Notes for the rule - optional

Returns: Created firewall rule information

Examples: # Allow HTTP from anywhere create_rule(group_id, "v4", "tcp", "0.0.0.0", 0, ctx, port="80")

# Allow SSH from specific subnet
create_rule(group_id, "v4", "tcp", "192.168.1.0", 24, ctx, port="22", notes="Office network")

# Allow ping from anywhere
create_rule(group_id, "v4", "icmp", "0.0.0.0", 0, ctx)

Input Schema

TableJSON Schema

Name	Required	Description	Default
`port`	No
`notes`	No
`source`	No
`subnet`	Yes
`ip_type`	Yes
`protocol`	Yes
`subnet_size`	Yes
`firewall_group_id`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Addedv1.0.1Sep 14, 2026

TDQS

A4.5/5.0

Behavior4/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses a conditional requirement (port needed for tcp/udp), notes optional fields (source, notes), and says it returns created rule information. The examples indicate real call patterns. It doesn't discuss idempotency or conflict behavior, but for a create operation the core behavior is clear.

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?

The Args/Returns/Examples structure is clear and scans well. With eight parameters plus examples, a longer description is justifiedholistically; there is no filler or redundant repetition, every line adds information.

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?

Given the tool has 8 parameters, no annotations, no enums, and only a minimal output schema, the description covers everything needed for correct invocation: parameter semantics, conditional requirements, examples, and return information. Nothing critical for the agent is missing.

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 description coverage is 0%, and the description fully compensates by documenting every parameter, including special conventions like '0.0.0.0' for any IPv4 and '::' for any IPv6, subnet size ranges, and port range syntax. The examples show exact parameter combinations that the JSON schema cannot convey.

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 opens with 'Create a new firewall rule' – a specific verb and object that names the exact operation and resource. It clearly distinguishes this from sibling tools like firewall_create_group or firewall_delete_rule. The examples reinforce that this tool adds a rule to an existing firewall group.

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 does not explicitly name alternatives such as firewall_setup_web_server_rules, but the Args section and examples give clear context for when this tool applies (creating a custom rule in a specified group). The purpose is unambiguous within the firewall_* sibling family, though the description could have pointed to alternative tools for common setups.

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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