The WordPress Theme.json Design Token Manager provides systematic control over design tokens in modern WordPress block themes. It reads and writes theme.json configurations using the WP_Theme_JSON_Resolver class, managing color palettes, font families, spacing presets, and custom CSS properties. The agent uses wp_get_global_settings() and wp_get_global_styles() to resolve merged settings across default, theme, and user layers. It supports design token versioning and migration between theme.json schema versions (v1 to v3) using WP_Theme_JSON_Schema::migrate(). The manager handles custom block style variations through the styles.blocks configuration and generates CSS custom properties via wp_get_global_stylesheet(). It validates token values against WordPress color and gradient formats, manages font face declarations through the Font Library API (wp_register_font_collection), and synchronizes tokens with Figma design files through the Figma REST API. Includes support for per-block settings overrides and appearance tools configuration.