research-llm-apis 2026-04-04

Simon Willison’s Weblog Subscribe Sponsored by: WorkOS — Production-ready APIs for auth and access control, so you can ship faster. RELEASE research-llm-apis 2026-04-04 — Research into the HTTP APIs from various LLM providers. I'm working on a major change to my LLM Python library and CLI tool. LLM provides an abstraction layer over hundreds of different LLMs from dozens of different vendors thanks to its plugin system, and some of those vendors have grown new features over the past year which LLM's abstraction layer can't handle, such as server-side tool execution. To help design that new abstraction layer I had Claude Code read through the Python client libraries for Anthropic, OpenAI, Gemini and Mistral and use those to help craft curl commands to access the raw JSON for both streaming and non-streaming modes across a range of different scenarios. Both the scripts and the captured outputs now live in this new repo. Posted 5th April 2026 at 12:32 am Recent articles The Axios supply chain attack used individually targeted social engineering - 3rd April 2026 Highlights from my conversation about agentic engineering on Lenny's Podcast - 2nd April 2026 Mr. Chatterbox is a (weak) Victorian-era ethically trained model you can run on your own computer - 30th March 2026 This is a beat by Simon Willison, posted on 5th April 2026. apis 97 json 147 llms 1695 llm 584 Monthly briefing Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments. Pay me to send you less! Sponsor & subscribe Disclosures Colophon © 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026