# Terraform Developer

> This skill provides expertise in developing Terraform configurations, Use when this capability is needed.

- Skill: `tomevault-io/terraform-developer` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/terraform-developer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/terraform-developer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/terraform-developer

---


# Terraform Developer

This skill provides expertise in developing Terraform configurations,
descriptors, modules, resources.

## Core Principles

- **Prefer resources over modules:** Favor simple resources for one-off
  configurations to keep designs flat. Introduce modules only when encapsulating
  complex, highly cohesive infrastructure or when reusability across multiple
  environments or projects is strictly required.
- **Loops over resources and modules:** Prefer `for` and `for_each` loops over
  repetitions.

## Best Practices

- **Terraform dependencies lockfile:** Generate Terraform dependency lockfiles
  running `terraform init`, and remind the user to do so and commit the lock
  file. If the infrastructure is shared across different operating systems or
  architectures, use
  `terraform providers lock -platform=linux_amd64 -platform=darwin_arm64 ...` to
  ensure all necessary platforms are covered.
- **Validation and formatting:** Run `terraform validate` to check for syntax
  errors and issues. Run `terraform fmt` (or `terraform fmt -recursive`) to
  automatically fix formatting issues.
- **Planning:** Run `terraform plan` after making modifications to verify the
  execution plan matches the intended structural changes.
- **Resource naming convention:** follow these rules when naming resources.
  - Use lowercase letters and underscores (`_`) to separate words when naming
    resources. Example: `server_vm`, not `server-vm`.
  - Avoid repeating the resource type in the resource name. For example, prefer
    `resource "aws_route_table" "public"` over
    `resource "aws_route_table" "public_route_table"`.
- **Variable definition:** follow these rules when defining variables.
  - If necessary, add a suffix to the variable name that denotes the unit.
    Example: `_gb` for gigabytes.
  - Add a `description` and a `type` when defining Terraform variables.
  - Implement variable `validation` if applicable. If you don't know how to
    validate the variable, ask the user.
- **Outputs definition:**
  - Store outputs in a file named `outputs.tf` within the module or Terraform
    service.
  - Don't pass input variables as outputs directly. To ensure that an output
    isn't evaluated until a resource is fully created, the output must reference
    an exported attribute of the created resource (e.g.,
    `value = google_compute_instance.web.id`).

### Data sources that reference variables

- When you define a variable, prefer initializing a datasource that exercises
  that variable and reference the datasource, instead of referencing the
  variable directly. This helps you validate the variable (in addition to the
  `validation` block in the variable definition), and ensures that a resource
  referencing the variable actually exists. For example:

  ```terraform
  variable "google_cloud_project_id" {
    description = "Google Cloud project id"
    type        = string
  }

  # Prefer this
  data "google_project" "google_cloud_project" {
    project_id = var.google_cloud_project_id
  }

  resource "google_project_service" "google_cloud_apis_good_example" {
    for_each = toset([
      "cloudresourcemanager.googleapis.com",
      "compute.googleapis.com",
    ])

    disable_dependent_services = false
    disable_on_destroy         = false
    project                    = data.google_project.google_cloud_project.project_id
    service                    = each.key
  }

  # Over this
  resource "google_project_service" "google_cloud_apis_bad_example" {
    for_each = toset([
      "cloudresourcemanager.googleapis.com",
      "compute.googleapis.com",
    ])

    disable_dependent_services = false
    disable_on_destroy         = false
    project                    = var.google_cloud_project_id
    service                    = each.key
  }

  ```

---
> Source: [ferrarimarco/dotfiles](https://github.com/ferrarimarco/dotfiles) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-06-15 -->