Building Your Own CLI Coding Agent with Pydantic-AI

1. pydantic-ai

   1 31 12,048 9.9 Python

   Agent Framework / shim to use Pydantic with LLMs

   

   I wanted to love pydantic AI as much as I love pydantic but the killer feature is pydantic-model-completion and weirdly.. it has always seemed to work better for me when I naively build it from scratch without pydantic AI.

   I haven't looked deeply into pydantic's implementation but this might be related to tool-usage vs completion [0], the backend LLM model, etc. All I know is that with the same LLM models, `openai.client.chat.completions` + a custom prompt to pass in the pydantic JSON schema + post-processing to instantiate SomePydanticModel(*json) creates objects successfully whereas vanilla pydantic-ai rarely does, regardless of the number of retries.

   I went with what works in my code, but didn't remove the pydantic-ai dependency completely because I'm hoping something changes. I'd say that getting dynamic prompt context by leveraging JSON schemas, model-and-field docs from pydantic, plus maybe other results from runtime-inspection (like the actual source-code) is obviously a very good idea. Many people want something like "fuzzy compilers" with structured output, not magical oracles that might return anything.

   Documentation is context, and even very fuzzy context is becoming a force multiplier. Similarly languages/frameworks with good support for runtime-inspection/reflection and have an ecosystem with strong tools for things like ASTs really should be the best things to pair with AI and agents.

   [0]: https://github.com/pydantic/pydantic-ai/issues/582

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3. rune-code

   2 1 1 8.3 Python

   An opinionated, forever ongoing personal project to make a useful, autonomous coding agent CLI.

   

   Pydantic-AI is lovely - I've been working on a forever, fun project to build a coding agent CLI for a year plus now. IMO it does make constructing any given agent very easy, though the lower level APIs are a little painful to use but they seem to be aware of that.

   https://github.com/caesarnine/rune-code

   Part of the reason I switched to it initially wasn't so much it's niceties versus just being disgusted at how poor the documentation/experience of using LiteLLM was and I thought the folks who make Pydantic would do a better job of the "universal" interface.

4. crabwalk

   3 15 69 7.3 Rust

   SQL transformation tool for DuckDB written in Rust

   

   we[0] have a pretty complex agent[1] running on Pydantic AI. The team is very responsive to bugs / feature requests. If I had to do it over again, I'd pick Pydantic AI again.

   0 - https://www.definite.app/

   1 - https://pydantic.dev/articles/building-data-team-with-pydant...

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