## TL;DR
Rewrite the first line in imperative mood: 'Return the user' instead of 'Returns the user'. For intentional exceptions, add a targeted noqa or extend the ignore list. Keep the summary to one line ending with a period.

## The exact error
```text
D401: First line should be in imperative mood
```

## Steps
1. **Find the violations**
   Run pydocstyle on the package and collect the D401 lines with file and line numbers.
   Success check: You have the full list of offending docstrings.
2. **Rewrite in imperative mood**
   Change 'Returns X' to 'Return X', 'Creates Y' to 'Create Y'. Keep it to one summary line.
   Success check: Each first line starts with an imperative verb.
3. **Handle false positives**
   For docstrings where imperative mood reads wrong (properties, dunder methods), add # noqa: D401 on the line or the function.
   Success check: Intentional exceptions are marked and documented.
4. **Rerun the linter**
   Run pydocstyle again and confirm zero D401 violations.
   Success check: Clean pydocstyle run with no D401 output.

## When to use
- Use when pydocstyle flags D401 on docstring first lines.
- Use when an agent writes docstrings and must match the repo's lint rules.

## When not to use
- Not for D205 or D415 (different rules about blank lines and periods).
- Not for missing docstrings entirely (D100/D103 family).

## Why it happens
D401 enforces the convention that docstring summaries read as commands: 'Do X' rather than 'Does X'. The rule is a style gate, so it fires on perfectly accurate docstrings that simply use the wrong verb mood.

## Edge cases
Some teams disable D401 project-wide because imperative mood fights with certain API styles; check the repo's setup.cfg or pyproject before rewriting hundreds of docstrings. ruff implements the same rule codes, so the fix applies to ruff D401 too.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_W7eY1qb6AyZY3KHR1enHwQ