Python: Allow for Agents as Kernel Functions

[moonbox3]

Motivation and Context

We're moving towards a pattern where Agents can be called as tools. We currently don't have this in Semantic Kernel Python.

This work builds off of the previous PR (#10828) but extends it to work with any SK Agent now that we have a bit more of a common invocation pattern (all agents take in messages kwarg). This also works now because each agent creates its own thread internally, if one isn't provided - so we don't need to worry about handling chat history for an OpenAI Assistant or an Azure AI Agent.

Description

Allow agents to be configured as Kernel Functions, which can then be used during Function Calling. We will advertise the Agent's name and either its description or instructions (if description is blank).

• Provide a sample where we show a triage agent (ChatCompletionAgent) calling either a billing agent (ChatCompletionAgent) or a refund agent (ChatCompletionAgent ) as part of a tool call to satisfy the user's query.
• Provide a sample where we show a triage agent (ChatCompletionAgent) calling either a billing agent (AzureAIAgent) or a refund agent (ChatCompletionAgent) to satisfy the user's query.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/agents
agent.py	158	29	82%	47, 54, 58, 67–78, 125, 130, 135, 140, 145, 149, 153, 157, 192–194, 222–229, 331–333, 400
semantic_kernel/functions
kernel_plugin.py	181	6	97%	393, 396, 409, 434, 455, 480
TOTAL	21233	2468	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3336	5 💤	0 ❌	0 🔥	1m 28s ⏱️