Oracle Index is an ingame clientside documentation mod, which is intended as an ingame view of content from moddedmc.wiki.
Mod developers can choose to include their wikis in their mods, and then use the Oracle Index mod to display them ingame. Press the wiki keybinding (default [H]) to open the oracle index screen. You don't need a special book item or anything. When exiting the screen, it'll remember where you left off.
You can only view the documentation of a mod if the mod is installed and the mod developer chose to include their documentation from moddedmc.wiki as Oracle Index wiki as well.
Mod Switching
On the left side of the screen, you'll see the navigation bar for the currently selected mod. To switch to another mod, simply click on the mods title bar above the navigation bar. A dropdown will open where you can select which mod to browse.
Item Links
Mod developers can add wiki links to ingame items. If a wiki page is available for an item, you'll see a small extra in the items tooltip. Hold the [ALT] button to open the corresponding wiki entry when seeing the items tooltip.
Language
Oracle Index automatically uses translated content for your exact Minecraft language when the wiki provides it. Page contents, navigation metadata, page titles, built-in controls, callouts, and status messages can all be translated.
Translated pages mirror the base page path under translated/<locale>/ in schema 1 wikis, or .translated/<locale>/ in legacy wikis. When a translated page or metadata file is missing, Oracle Index falls back to the base-language resource.
Search currently indexes the base-language page text. Results still open the translated page when one is available, and displayed page titles use the active language.