Simon Willison reported the announcement on October 22, 2026, quoting Anthropic’s statement that the format should remain open, community-driven, and vendor-neutral.
AAIF was co-founded by Anthropic, Block, and OpenAI. Anthropic had previously donated the Model Context Protocol specification to the same foundation. Agent Skills is an open format for agent skill packages; its specification defines a required SKILL.md file with YAML frontmatter and Markdown instructions, with optional scripts, references, and assets.
The specification describes staged loading of skill information: metadata first, instructions when a skill is activated, and additional resources as needed. It recommends instructions below 5,000 tokens and a SKILL.md under 500 lines.
The supplied source does not establish AAIF's future governance process, which products will implement the standard, or any compliance requirements for Agent Skills.