Teaching coding agents the differential DuckDB extension with an Agent Skill

Coding agents are good at DuckDB, as long as the DuckDB they need is the one from their training data. A freshly released extension is a different story: the agent has never seen its functions, so it guesses, and the guesses look convincing. The new Agent Skill for duckdb-differential closes that gap. Two days ago I wrote about duckdb-differential 1.0: versioned DuckDB databases with snapshots, branches and time travel, replicated through S3 with followers, WAL shipping, failover and shared writers. All of it is SQL, but it’s new SQL. No model has seen differential_recover_branch or FOLLOW true in its training data, and DuckDB 2.0 is new as well. So instead of hoping the agent guesses right, the repository now ships the knowledge with the code. The problem with brand-new extensions# Ask an agent to “branch my DuckDB database and try a migration on it” without any context, and you typically get one of three things: a copy of the .duckdb file, a plausible-looking function that doesn’t…