Field Descriptions via Base Field Overrides

What: To add help text or descriptions to base fields (e.g., node title), use core.base_field_override.node.{bundle}.{field}.yml config — not hook_form_alter().

Rationale: Config is exportable, doesn't require custom module code, and survives module changes. hook_form_alter() requires a custom module, runs on every form build (a small but real cost), needs careful conditional checks to avoid affecting other forms, and adds a maintenance surface. Base field overrides are core's built-in mechanism for exactly this use case.

When it applies: Adding help text, default values, label changes, or required-flag changes to base fields (title, status, promoted, etc.) on a per-bundle basis.

Example:

# Right — config-only override
# config/sync/core.base_field_override.node.article.title.yml
langcode: en
status: true
field_name: title
entity_type: node
bundle: article
label: Headline
description: 'The article headline as it appears in listings and at the top of the article page.'
required: true
default_value: []
default_value_callback: ''
settings: {  }

// Wrong — custom module + form_alter
function mymodule_form_node_article_form_alter(&$form, FormStateInterface $form_state) {
  $form['title']['widget'][0]['value']['#description'] =
    t('The article headline as it appears in listings and at the top of the article page.');
}