Add to_cli() method to Agent

[AndrewHannigan]

Overview

Exposes existing CLI functionality as a method on Agent. This allows users to use CLI with custom Agents.

Related issue: #1595

Demo for Agent.run_cli()

Script

pydantic-ai add-agent-cli % cat /Users/andrewhannigan/Downloads/agent_cli.py
from pydantic_ai import Agent

agent = Agent("openai:gpt-4o")


@agent.system_prompt
def system_prompt() -> str:
    return "Your name is Alice."


agent.run_cli()

Result

pydantic-ai add-agent-cli % uv run /Users/andrewhannigan/Downloads/agent_cli.py
pai - PydanticAI CLI v0.1.10.dev1+1e56101 using openai:gpt-4o
pai ➤ what is your name
My name is Alice. How can I assist you today?

Demo for pai --agent

pydantic-ai add-agent-cli % echo "from pydantic_ai import Agent\nagent = Agent(system_prompt='Your name is Bob.')" > pydantic_ai_slim/pydantic_ai/my_agent.py
pydantic-ai add-agent-cli % uv run pai -a pydantic_ai.my_agent:agent "what is your name"
pai - PydanticAI CLI v0.1.10.dev1+1e56101 using openai:gpt-4o
Using custom agent: pydantic_ai.my_agent:agent
My name is Bob. How can I assist you today?

[hyperlint-ai]

PR Change Summary

Exposed the existing CLI functionality as a method on the Agent, allowing users to utilize CLI with custom Agents.

• Introduced the run_cli() method on the Agent class for direct CLI access.
• Updated documentation to include usage examples for custom agents.
• Enhanced CLI documentation with installation and usage instructions.

Modified Files

• docs/cli.md

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[AndrewHannigan]

@samuelcolvin @Kludex any concerns merging this before #1504? This PR is a minor refactor, mainly just allows cli() to accept an Agent object. The only references to pai in this PR are in a few lines of documentation so I think the conflict risk is low.

[Kludex]

agent doesn't need to be a parameter here.

[AndrewHannigan]

@Kludex It's necessary to support the run_cli() method here

[AndrewHannigan]

We could also remove run_cli() and just align on --agent mymodule.submodule:my_agent as the interface if that's preferable, let me know your thoughts.