DOC: Add AGENTS.md with basic type and docstring guidelines (#62541)

Author: jzwick

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,3 +3,4 @@
 - [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
 - [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
 - [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.
+- [ ] If I used AI to develop this pull request, I prompted it to follow `AGENTS.md`.

AGENTS.md

@@ -0,0 +1,48 @@
+# pandas Agent Instructions
+
+## Project Overview
+`pandas` is an open source, BSD-licensed library providing high-performance, easy-to-use data structures and data analysis tools for the Python programming language.
+
+## Purpose
+- Assist contributors by suggesting code changes, tests, and documentation edits for the pandas repository while preserving stability and compatibility.
+
+## Persona & Tone
+- Concise, neutral, code-focused. Prioritize correctness, readability, and tests.
+
+## Project Guidelines
+- Be sure to follow all guidelines for contributing to the codebase specified at https://pandas.pydata.org/docs/development/contributing_codebase.html
+- These guidelines are also available in the following local files, which should be loaded into context and adhered to
+    - doc/source/development/contributing_codebase.rst
+    - doc/source/development/contributing_docstring.rst
+    - doc/source/development/contributing_documentation.rst
+    - doc/source/development/contributing.rst
+
+## Decision heuristics
+- Favor small, backward-compatible changes with tests.
+- If a change would be breaking, propose it behind a deprecation path and document the rationale.
+- Prefer readability over micro-optimizations unless benchmarks are requested.
+- Add tests for behavioral changes; update docs only after code change is final.
+
+## Type hints guidance (summary)
+- Prefer PEP 484 style and types in pandas._typing when appropriate.
+- Avoid unnecessary use of typing.cast; prefer refactors that convey types to type-checkers.
+- Use builtin generics (list, dict) when possible.
+
+## Docstring guidance (summary)
+- Follow NumPy / numpydoc conventions used across the repo: short summary, extended summary, Parameters, Returns/Yields, See Also, Notes, Examples.
+- Ensure examples are deterministic, import numpy/pandas as documented, and pass doctest rules used by docs validation.
+- Preserve formatting rules: triple double-quotes, no blank line before/after docstring, parameter formatting ("name : type, default ..."), types and examples conventions.
+
+## Pull Requests (summary)
+- Pull request titles should be descriptive and include one of the following prefixes:
+    - ENH: Enhancement, new functionality
+    - BUG: Bug fix
+    - DOC: Additions/updates to documentation
+    - TST: Additions/updates to tests
+    - BLD: Updates to the build process/scripts
+    - PERF: Performance improvement
+    - TYP: Type annotations
+    - CLN: Code cleanup
+- Pull request descriptions should follow the template, and **succinctly** describe the change being made. Usually a few sentences is sufficient.
+- Pull requests which are resolving an existing Github Issue should include a link to the issue in the PR Description.
+- Do not add summaries or additional comments to individual commit messages. The single PR description is sufficient.