To declare an output in a custom GitHub Action, you add an outputs block to your action.yml metadata file.
Here is the minimal yaml syntax:
outputs:
foo:
description: 'A description is required'
Use code with caution.
Note: The description field is mandatory in the metadata file, even if it is brief. To actually assign a value to this output during execution, you would then use the following command in your script:
echo "charlemagne=your_value" >> $GITHUB_OUTPUT
Reference:
https://oneuptime.com/blog/post/2026-01-30-github-actions-action-outputs/view

Setting exit codes for actions
You can use exit codes to set the status of an action. GitHub displays statuses to indicate passing or failing actions.
About exit codes
GitHub uses the exit code to set the action's check run status, which can be success or failure.
* Exit status: 0
Check run status: success
The action completed successfully and other tasks that depend on it can begin.
* Exit status: Nonzero value (any integer but 0)
Check run status: failure
Any other exit code indicates the action failed. When an action fails, all concurrent actions are canceled and future actions are skipped. The check run and check suite both get a failure status.
Reference:
https://docs.github.com/en/actions/how-tos/create-and-publish-actions/set-exit-codes

To use a specific API key in your GitHub Actions workflow, you can store it as a Repository Secret and reference it using the secrets context in your YAML file. This ensures the key is encrypted and masked in your workflow logs.
1. Store the API Key as a Secret
Navigate to your repository on GitHub.com.
Click Settings > Secrets and variables > Actions.
Select the Secrets tab and click New repository secret.
In the Name field, enter a descriptive identifier (e.g., MY_API_KEY).
Rules: Use only alphanumeric characters or underscores; cannot start with a number or GITHUB_.
In the Secret field, paste your API key value and click Add secret.
2. Reference the Secret in your YAML File
In your .github/workflows/your-workflow.yml file, access the secret using the syntax
${{ secrets.NAME_OF_SECRET }}. It is a best practice to map it to an environment variable within a specific step rather than echoing it directly.
Example Workflow in yaml:
name: Use API Key Example
on: [push]
jobs:
my-job:
runs-on: ubuntu-latest
steps:
- name: Run script with API Key
# Map the secret to an environment variable for the runner
env:
API_KEY: ${{ secrets.MY_API_KEY }}
run: |
# Use the environment variable in your commands
curl -H "Authorization: Bearer $API_KEY" https://api.example.com
Reference:
https://docs.github.com/actions/security-guides/using-secrets-in-github-actions

The check_run event is triggered when a check (such as a code quality check) completes, including when the status of a check changes. By adding this event as a trigger, you can initiate a follow-up workflow when the code quality integration finishes its checks.
Reference:
https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows

To output a specific debug message in GitHub Actions, use the ::debug:: workflow command.
Usage Syntax
You can issue this command by printing it to standard output (stdout) during a workflow step:
echo "::debug::{message}"
Reference:
https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-commands