OKF (§8) defines index.md as an optional directory listing that enumerates the directory's contents, enabling progressive disclosure — letting a human or agent see what is available before opening individual documents. It is one of the two reserved filenames.

Changed from v0.1. This section was §6 in v0.1; it is §8 in v0.2. The rules are unchanged.

Rules

• An index.md MAY appear in any directory, including the bundle root.
• It contains no frontmatter — with the single exception that the root index.md MAY carry frontmatter to declare okf_version.
• It groups concept links under section headings, each link followed by the concept's short description (SHOULD reuse the linked concept's frontmatter description).

Format

# Section / Group Heading

* [Title 1](relative-or-absolute-url) - short description of item 1
* [Title 2](another-url) - short description of item 2

# Another Section

* [Subdirectory](subdir/) - short description of the subdirectory

The root index of this bundle and each section index (e.g. concepts, this spec/index.md) follow exactly this shape. Producers MAY generate index.md automatically; consumers MAY synthesize one on the fly when none is present. Index files are maintained on every ingest; keeping them current is what makes progressive-disclosure navigation reliable. Because index files are optional, consumers MUST NOT reject a bundle that lacks them.

Citations

1. OKF Specification (SPEC.md)