terraform-style-guide
Generate Terraform HCL code following HashiCorp's official style conventions and best practices. Use when writing, reviewing, or generating Terraform configurations.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/hashicorp/agent-skills --skill terraform-style-guide- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads terraform-style-guide automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
Terraform Style Guide
Generate and maintain Terraform code following HashiCorp's official style conventions and best practices.
Reference: HashiCorp Terraform Style Guide
Code Generation Strategy
When generating Terraform code:
- Start with provider configuration and version constraints
- Create data sources before dependent resources
- Build resources in dependency order
- Add outputs for key resource attributes
- Use variables for all configurable values
File Organization
| File | Purpose |
|---|---|
terraform.tf | Terraform and provider version requirements |
providers.tf | Provider configurations |
main.tf | Primary resources and data sources |
variables.tf | Input variable declarations (alphabetical) |
outputs.tf | Output value declarations (alphabetical) |
locals.tf | Local value declarations |
Example Structure
# terraform.tf
terraform {
required_version = ">= 1.14"
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 6.0"
}
}
}
# variables.tf
variable "environment" {
description = "Target deployment environment"
type = string
validation {
condition = contains(["dev", "staging", "prod"], var.environment)
error_message = "Environment must be dev, staging, or prod."
}
}
# locals.tf
locals {
common_tags = {
Environment = var.environment
ManagedBy = "Terraform"
}
}
# main.tf
resource "aws_vpc" "main" {
cidr_block = var.vpc_cidr
enable_dns_hostnames = true
tags = merge(local.common_tags, {
Name = "${var.project_name}-${var.environment}-vpc"
})
}
# outputs.tf
output "vpc_id" {
description = "ID of the created VPC"
value = aws_vpc.main.id
}
Code Formatting
Indentation and Alignment
- Use two spaces per nesting level (no tabs)
- Align equals signs for consecutive arguments
resource "aws_instance" "web" {
ami = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
subnet_id = "subnet-12345678"
tags = {
Name = "web-server"
Environment = "production"
}
}
Block Organization
Arguments precede blocks, with meta-arguments first:
resource "aws_instance" "example" {
# Meta-arguments
count = 3
# Arguments
ami = "ami-0c55b159cbfafe1f0"
instance_type = "t2.micro"
# Blocks
root_block_device {
volume_size = 20
}
# Lifecycle last
lifecycle {
create_before_destroy = true
}
}
Naming Conventions
- Use lowercase with underscores for all names
- Use descriptive nouns excluding the resource type
- Be specific and meaningful
- Resource names must be singular, not plural
- Default to
mainfor resources where a specific descriptive name is redundant or unavailable, provided only one instance exists
# Bad
resource "aws_instance" "webAPI-aws-instance" {}
resource "aws_instance" "web_apis" {}
variable "name" {}
# Good
resource "aws_instance" "web_api" {}
resource "aws_vpc" "main" {}
variable "application_name" {}
Variables
Every variable must include type and description:
variable "instance_type" {
description = "EC2 instance type for the web server"
type = string
default = "t2.micro"
validation {
condition = contains(["t2.micro", "t2.small", "t2.medium"], var.instance_type)
error_message = "Instance type must be t2.micro, t2.small, or t2.medium."
}
}
variable "database_password" {
description = "Password for the database admin user"
type = string
sensitive = true
}
Outputs
Every output must include description:
output "instance_id" {
description = "ID of the EC2 instance"
value = aws_instance.web.id
}
output "database_password" {
description = "Database administrator password"
value = aws_db_instance.main.password
sensitive = true
}
Dynamic Resource Creation
Prefer for_each over count
# Bad - count for multiple resources
resource "aws_instance" "web" {
count = var.instance_count
tags = { Name = "web-${count.index}" }
}
# Good - for_each with named instances
variable "instance_names" {
type = set(string)
default = ["web-1", "web-2", "web-3"]
}
resource "aws_instance" "web" {
for_each = var.instance_names
tags = { Name = each.key }
}
count for Conditional Creation
resource "aws_cloudwatch_metric_alarm" "cpu" {
count = var.enable_monitoring ? 1 : 0
alarm_name = "high-cpu-usage"
threshold = 80
}
Security Best Practices
Refer to SECURITY.md. It includes guidance on encrypting resources, preventing sensitive data in state, and secure configurations.
Version Pinning
terraform {
required_version = ">= 1.14"
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 6.0"
}
}
}
Use the latest major version of each provider and the latest minor version of Terraform, unless otherwise constrained by a dependency lock file or by other modules used by the configuration.
Version constraint operators:
= 1.0.0- Exact version>= 1.0.0- Greater than or equal~> 1.0- Allow rightmost component to increment>= 1.0, < 2.0- Version range
Provider Configuration
provider "aws" {
region = "us-west-2"
default_tags {
tags = {
ManagedBy = "Terraform"
Project = var.project_name
}
}
}
# Aliased provider for multi-region
provider "aws" {
alias = "east"
region = "us-east-1"
}
Version Control
Never commit:
terraform.tfstate,terraform.tfstate.backup.terraform/directory*.tfplan.tfvarsfiles with sensitive data
Always commit:
- All
.tfconfiguration files .terraform.lock.hcl(dependency lock file)
Validation Tools
Run before committing:
terraform fmt -recursive
terraform validate
Additional tools:
tflint- Linting and best practicescheckov/tfsec- Security scanning
Code Review Checklist
- Code formatted with
terraform fmt - Configuration validated with
terraform validate - Files organized according to standard structure
- All variables have type and description
- All outputs have descriptions
- Resource names use descriptive nouns with underscores
- Version constraints pinned explicitly
- Sensitive values marked with
sensitive = true - No hardcoded credentials or secrets
- Security best practices applied
Based on: HashiCorp Terraform Style Guide
FAQ
What does the terraform-style-guide skill do?
Generate Terraform HCL code following HashiCorp's official style conventions and best practices. Use when writing, reviewing, or generating Terraform configurations.
How do I install terraform-style-guide?
Run npx skills add https://github.com/hashicorp/agent-skills --skill terraform-style-guide in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/terraform-style-guide/ (personal) or .claude/skills/terraform-style-guide/ (project).
Which AI agents can use terraform-style-guide?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is terraform-style-guide safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed; Runlayer passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains terraform-style-guide?
It is published by hashicorp in hashicorp/agent-skills, and it is an official skill from the maker of the technology it covers. It has 12,616 recorded installs.
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