feat: Add SkillsToolset to enable Haystack's Agent to read Skills

[sjrl]

Related Issues

• fixes https://github.com/deepset-ai/haystack-private/issues/386

Proposed Changes:

How did you test it?

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
haystack-docs	Ignored	Preview	Jun 1, 2026 12:18pm

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Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/components/agents
agent.py					209, 211-212
haystack/tools
__init__.py
tool.py
toolset.py					189
haystack/tools/skills
__init__.py
skill_toolset.py					53, 139, 201-202
Project Total

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[sjrl]

After talking with @tstadel we agreed to drop the system_prompt_contribution addition for now and instead bake in more relevant instructions into the tool descriptions themselves.