Ask Claude to Document Every Environment Variable Your App Actually Uses

Environment variables are the most under-documented part of any project. The .env.example file lists names and placeholder values, but never explains what they do, which are required, or what breaks if they're wrong. Claude reads your code and writes the documentation.

Search the entire codebase for every environment variable reference 
(process.env, env(), getenv, os.environ). For each one, document what 
it controls, where it's used, whether it's required, and what the 
default value is if not set.

Claude produces a clear reference:

| Variable | Required | Default | Description |
|----------|----------|---------|-------------|
| DATABASE_URL | Yes | — | PostgreSQL connection string |
| REDIS_URL | No | localhost:6379 | Redis cache connection |
| MAIL_FROM | Yes | — | Sender address for transactional emails |
| RATE_LIMIT_PER_MINUTE | No | 60 | API rate limit per authenticated user |
| FEATURE_NEW_CHECKOUT | No | false | Enable the new checkout flow |

Target specific documentation needs:

# Find undocumented variables
Compare the env vars used in code against what's in .env.example. 
Which ones are referenced in code but missing from the example file?

# Group by subsystem
Document the env vars grouped by what they configure — database, cache, 
mail, auth, feature flags, third-party services.

# Add validation hints
For each variable, note the expected format — is it a URL, a number, 
a boolean, a comma-separated list? This helps catch config errors 
before they cause runtime failures.

After generating the docs, ask Claude to keep them in sync:

Add this env var documentation as a section in the README. 
Also update .env.example with comments explaining each variable.

Undocumented environment variables are configuration landmines — let Claude find every one and explain what it does before someone misconfigures it.

via Claude Code