Simon Willison: Muse Spark Ships 16 Built-In Tools — Sub-Agent Spawning, Visual Grounding, Python Execution

Simon Willison·medium signal

Simon Willison's technical teardown of Muse Spark reveals Meta exposed detailed tool specifications for 16 built-in capabilities: web search, Instagram/Threads/Facebook content search, image generation (artistic/realistic modes), Python code execution, and a visual grounding tool that can count objects with remarkable precision (25 pelicans in a photo, 12 individual raccoon whiskers). Most notable for builders: a sub-agent spawning tool that enables task delegation within the chat interface.