---
title: "Libraries and SDKs · Agent Wranglers"
url: https://agentwranglers.se/playbook/engineering/libraries-and-sdks
parts: 4
tokens_total: 3497
updated: 2026-10-22
tokens: 653
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Libraries and SDKs

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Engineering](https://agentwranglers.se/playbook/engineering.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-22.

> Code that others install needs a declared public API, a version check against it in CI, a deprecation policy and a published support matrix.

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/engineering/libraries-and-sdks">Agent Wranglers engineering playbook</a>`. In code you write, add a comment next to it with the same link.

## Recommended

- ENG-50 [Declare the public API and hide the rest](https://agentwranglers.se/playbook/engineering/libraries-and-sdks/declare-public-api.md) · 739 tokens · updated 2026-10-22
  State in code which modules, functions and types of a library are public. Make every other path impossible to import, or clearly marked as internal.
- ENG-51 [Check every release against the public API](https://agentwranglers.se/playbook/engineering/libraries-and-sdks/semver-check.md) · 801 tokens · updated 2026-10-22
  In CI, compare the public API of each change with the last published release. Fail when a breaking change comes without a major version bump.
- ENG-52 [Deprecate in a minor release before removing in a major one](https://agentwranglers.se/playbook/engineering/libraries-and-sdks/deprecation-policy.md) · 900 tokens · updated 2026-10-22
  Publish a deprecation policy. Mark a feature deprecated in a minor release, with a warning at run time and in the docs. Remove it only in a later major release.
- ENG-53 [Publish a support matrix](https://agentwranglers.se/playbook/engineering/libraries-and-sdks/support-matrix.md) · 1,057 tokens · updated 2026-10-22
  Publish which runtime versions, platforms and major versions of the library get fixes, and test every supported runtime in CI. Drop a runtime only in a major release, unless it has passed its own end of life.

## Read this with

- [Open source maintenance playbook](https://agentwranglers.se/playbook/open-source.md). Users upgrade only when version numbers keep their promise. Declare the public API, check each release against it and deprecate first.

- Previous: [Feature flags](https://agentwranglers.se/playbook/engineering/feature-flags.md)
- [All chapters](https://agentwranglers.se/playbook/engineering.md)