diff --git a/docs/spec.md b/docs/spec.md
index 41b6d085..5ff34173 100644
--- a/docs/spec.md
+++ b/docs/spec.md
@@ -59,18 +59,24 @@ components:
 
 The `<scale-level>` placeholder represents a named level in a sizing or spacing scale. Common level names include `xs`, `sm`, `md`, `lg`, `xl`, and `full`. Any descriptive string key is valid.
 
-**Color**: A color value is any valid CSS color string. Supported formats include:
+**Color**: A color value is any valid CSS color string.
 
-* Hex: `#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`
-* Named colors: `red`, `cornflowerblue`, `transparent`
-* Functional: `rgb()`, `rgba()`, `hsl()`, `hsla()`, `hwb()`
-* Wide-gamut: `oklch()`, `oklab()`, `lch()`, `lab()`
-* Mixing: `color-mix(in srgb, ...)`
+Supported formats include:
+
+- Hex: `#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`
+- Named colors: `red`, `cornflowerblue`, `transparent`
+- Functional: `rgb()`, `rgba()`, `hsl()`, `hsla()`, `hwb()`
+- Wide-gamut: `oklch()`, `oklab()`, `lch()`, `lab()`
+- Mixing: `color-mix(in srgb, ...)`
 
 All color values are internally converted to sRGB for WCAG contrast checking. The original format is preserved for display and export.
 
 Hex notation (`#RRGGBB`) remains the recommended default for simplicity and broad tooling support.
 
+**Dimension**: A dimension value is a string with a unit suffix.
+
+Valid units are: px, em, rem.
+
 - `fontFamily` (string)
 - `fontSize` (Dimension)
 - `fontWeight` (number) - A numeric font weight value (e.g., `400`, `700`). In YAML, this may be expressed as either a bare number or a quoted string; both are equivalent.
@@ -81,8 +87,6 @@ Hex notation (`#RRGGBB`) remains the recommended default for simplicity and broa
 - `fontVariation` (string) - configures
   [`font-variation-settings`](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/font-variation-settings).
 
-**Dimension**: A dimension value is a string with a unit suffix. Valid units are: px, em, rem.
-
 **Token References**: A token reference must be wrapped in curly braces, and contain an object path to another value in the YAML tree. For most token groups, the reference must point to a primitive value (e.g., `colors.primary-60`), not a group (e.g., `colors`). Within the `components` section, references to composite values (e.g., `{typography.label-md}`) are permitted.
 
 # Sections
diff --git a/packages/cli/src/linter/spec-config.test.ts b/packages/cli/src/linter/spec-config.test.ts
index 0115b371..b1ab7cbc 100644
--- a/packages/cli/src/linter/spec-config.test.ts
+++ b/packages/cli/src/linter/spec-config.test.ts
@@ -18,6 +18,7 @@ import {
   loadSpecConfig,
   getSpecConfig,
   STANDARD_UNITS,
+  SPEC_TYPES,
   SECTIONS,
   TYPOGRAPHY_PROPERTIES,
   COMPONENT_SUB_TOKENS,
@@ -159,6 +160,14 @@ describe('spec-config structural invariants', () => {
     expect(new Set(STANDARD_UNITS).size).toBe(STANDARD_UNITS.length);
   });
 
+  it('primitive type definitions are non-empty', () => {
+    expect(Object.keys(SPEC_TYPES).length).toBeGreaterThan(0);
+    for (const [name, typeDef] of Object.entries(SPEC_TYPES)) {
+      expect(name.length).toBeGreaterThan(0);
+      expect(typeDef.description.length).toBeGreaterThan(0);
+    }
+  });
+
   it('recommended token categories are non-empty', () => {
     for (const [category, tokens] of Object.entries(RECOMMENDED_TOKENS)) {
       expect(tokens.length).toBeGreaterThan(0);
diff --git a/packages/cli/src/linter/spec-config.ts b/packages/cli/src/linter/spec-config.ts
index b146a47b..30339a19 100644
--- a/packages/cli/src/linter/spec-config.ts
+++ b/packages/cli/src/linter/spec-config.ts
@@ -38,6 +38,14 @@ const PropertyDefSchema = z.object({
   description: z.string().optional(),
 });
 
+const TypeDefSchema = z.object({
+  description: z.string(),
+  formats: z.array(z.string()).optional(),
+  units: z.array(z.string()).optional(),
+  note: z.string().optional(),
+  recommendation: z.string().optional(),
+});
+
 const ConfigSchema = z.object({
   version: z.string(),
   limits: z.object({
@@ -45,6 +53,7 @@ const ConfigSchema = z.object({
     max_reference_depth: z.number().default(10),
   }).default({}),
   units: z.array(z.string()).min(1),
+  types: z.record(z.string(), TypeDefSchema),
   sections: z.array(z.object({
     canonical: z.string(),
     aliases: z.array(z.string()).optional(),
@@ -112,6 +121,19 @@ export interface ComponentSubTokenDef {
   description?: string | undefined;
 }
 
+export interface TypeDef {
+  /** One-sentence definition for the type. */
+  description: string;
+  /** Accepted formats rendered as a bullet list in the generated spec. */
+  formats?: readonly string[] | undefined;
+  /** Accepted units for dimensional types. */
+  units?: readonly string[] | undefined;
+  /** Additional normative or implementation note. */
+  note?: string | undefined;
+  /** Non-normative authoring recommendation. */
+  recommendation?: string | undefined;
+}
+
 // ── Constant exports ─────────────────────────────────────────────────
 // These are eagerly initialized from the lazy singleton on first import.
 // The singleton cache ensures the YAML file is read exactly once.
@@ -129,6 +151,9 @@ export const MAX_REFERENCE_DEPTH = config.limits.max_reference_depth;
 export const STANDARD_UNITS = config.units;
 export type StandardUnit = (typeof STANDARD_UNITS)[number];
 
+/** Primitive type definitions rendered into the generated spec. */
+export const SPEC_TYPES: Record<string, TypeDef> = config.types;
+
 export const SECTIONS = config.sections;
 
 export const TYPOGRAPHY_PROPERTIES: readonly TypographyPropertyDef[] = config.typography_properties;
@@ -175,6 +200,7 @@ export interface SpecConfig {
   MAX_TOKEN_NESTING_DEPTH: typeof MAX_TOKEN_NESTING_DEPTH;
   MAX_REFERENCE_DEPTH: typeof MAX_REFERENCE_DEPTH;
   STANDARD_UNITS: typeof STANDARD_UNITS;
+  SPEC_TYPES: typeof SPEC_TYPES;
   SECTIONS: typeof SECTIONS;
   TYPOGRAPHY_PROPERTIES: typeof TYPOGRAPHY_PROPERTIES;
   COMPONENT_SUB_TOKENS: typeof COMPONENT_SUB_TOKENS;
@@ -189,6 +215,7 @@ export const SPEC_CONFIG: SpecConfig = {
   MAX_TOKEN_NESTING_DEPTH,
   MAX_REFERENCE_DEPTH,
   STANDARD_UNITS,
+  SPEC_TYPES,
   SECTIONS,
   TYPOGRAPHY_PROPERTIES,
   COMPONENT_SUB_TOKENS,
diff --git a/packages/cli/src/linter/spec-config.yaml b/packages/cli/src/linter/spec-config.yaml
index 67dfa143..478be8f9 100644
--- a/packages/cli/src/linter/spec-config.yaml
+++ b/packages/cli/src/linter/spec-config.yaml
@@ -28,6 +28,24 @@ units:
   - em
   - rem
 
+types:
+  Color:
+    description: A color value is any valid CSS color string.
+    formats:
+      - "Hex: `#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`"
+      - "Named colors: `red`, `cornflowerblue`, `transparent`"
+      - "Functional: `rgb()`, `rgba()`, `hsl()`, `hsla()`, `hwb()`"
+      - "Wide-gamut: `oklch()`, `oklab()`, `lch()`, `lab()`"
+      - "Mixing: `color-mix(in srgb, ...)`"
+    note: All color values are internally converted to sRGB for WCAG contrast checking. The original format is preserved for display and export.
+    recommendation: Hex notation (`#RRGGBB`) remains the recommended default for simplicity and broad tooling support.
+  Dimension:
+    description: A dimension value is a string with a unit suffix.
+    units:
+      - px
+      - em
+      - rem
+
 sections:
   - canonical: Overview
     aliases:
diff --git a/packages/cli/src/linter/spec-gen/compiler.test.ts b/packages/cli/src/linter/spec-gen/compiler.test.ts
index 656c796d..ce260aa4 100644
--- a/packages/cli/src/linter/spec-gen/compiler.test.ts
+++ b/packages/cli/src/linter/spec-gen/compiler.test.ts
@@ -70,6 +70,7 @@ describe('compileMdx', () => {
       typographyExample: () => renderers.typographyExample(cfg),
       componentsExample: () => renderers.componentsExample(cfg),
       typographyPropertyList: () => renderers.typographyPropertyList(cfg),
+      typeDefinitions: () => renderers.typeDefinitions(cfg),
       sectionOrderList: () => renderers.sectionOrderList(cfg),
       componentSubTokenList: () => renderers.componentSubTokenList(cfg),
       recommendedTokens: () => renderers.recommendedTokens(cfg),
diff --git a/packages/cli/src/linter/spec-gen/generate.ts b/packages/cli/src/linter/spec-gen/generate.ts
index b622ec37..b397ddf4 100644
--- a/packages/cli/src/linter/spec-gen/generate.ts
+++ b/packages/cli/src/linter/spec-gen/generate.ts
@@ -46,6 +46,7 @@ async function main() {
     typographyExample: () => renderers.typographyExample(cfg),
     componentsExample: () => renderers.componentsExample(cfg),
     typographyPropertyList: () => renderers.typographyPropertyList(cfg),
+    typeDefinitions: () => renderers.typeDefinitions(cfg),
     sectionOrderList: () => renderers.sectionOrderList(cfg),
     componentSubTokenList: () => renderers.componentSubTokenList(cfg),
     recommendedTokens: () => renderers.recommendedTokens(cfg),
diff --git a/packages/cli/src/linter/spec-gen/renderers.ts b/packages/cli/src/linter/spec-gen/renderers.ts
index c7cfb985..9e0354d6 100644
--- a/packages/cli/src/linter/spec-gen/renderers.ts
+++ b/packages/cli/src/linter/spec-gen/renderers.ts
@@ -19,7 +19,7 @@
  * Each function returns a ready-to-embed markdown string.
  */
 
-import type { SpecConfig, TypographyPropertyDef, SectionDef, ComponentSubTokenDef } from '../spec-config.js';
+import type { SpecConfig, TypographyPropertyDef, SectionDef, ComponentSubTokenDef, TypeDef } from '../spec-config.js';
 
 // ── YAML code block helpers ─────────────────────────────────────
 
@@ -95,6 +95,36 @@ export function typographyPropertyList(config: SpecConfig): string {
   ).join('\n');
 }
 
+/** Primitive type definitions for the schema section. */
+export function typeDefinitions(config: SpecConfig): string {
+  return Object.entries(config.SPEC_TYPES)
+    .map(([name, typeDef]) => typeDefinition(name, typeDef))
+    .join('\n\n');
+}
+
+function typeDefinition(name: string, typeDef: TypeDef): string {
+  const lines = [`**${name}**: ${typeDef.description}`];
+
+  if (typeDef.formats?.length) {
+    lines.push('', 'Supported formats include:', '');
+    lines.push(...typeDef.formats.map(format => `- ${format}`));
+  }
+
+  if (typeDef.units?.length) {
+    lines.push('', `Valid units are: ${typeDef.units.join(', ')}.`);
+  }
+
+  if (typeDef.note) {
+    lines.push('', typeDef.note);
+  }
+
+  if (typeDef.recommendation) {
+    lines.push('', typeDef.recommendation);
+  }
+
+  return lines.join('\n');
+}
+
 /** Numbered section order list with aliases. */
 export function sectionOrderList(config: SpecConfig): string {
   return config.SECTIONS.map((s: SectionDef, i: number) => {
diff --git a/packages/cli/src/linter/spec-gen/spec-helpers.test.ts b/packages/cli/src/linter/spec-gen/spec-helpers.test.ts
index 926bac71..4c3ae081 100644
--- a/packages/cli/src/linter/spec-gen/spec-helpers.test.ts
+++ b/packages/cli/src/linter/spec-gen/spec-helpers.test.ts
@@ -58,6 +58,12 @@ describe('getSpecContent', () => {
     expect(content.length).toBeGreaterThan(1000);
   });
 
+  it('renders primitive type definitions from spec config', () => {
+    const content = getSpecContent();
+    expect(content).toContain('**Color**: A color value is any valid CSS color string.');
+    expect(content).toContain('**Dimension**: A dimension value is a string with a unit suffix.');
+  });
+
   it('accepts an explicit specPath override', () => {
     // This tests the explicit-path contract. If someone passes a path,
     // it should use that path exactly — no guessing.
diff --git a/packages/cli/src/linter/spec-gen/spec.mdx b/packages/cli/src/linter/spec-gen/spec.mdx
index 44064d5c..b82bbc51 100644
--- a/packages/cli/src/linter/spec-gen/spec.mdx
+++ b/packages/cli/src/linter/spec-gen/spec.mdx
@@ -1,5 +1,5 @@
-import { SPEC_VERSION, STANDARD_UNITS, SECTIONS, TYPOGRAPHY_PROPERTIES, COMPONENT_SUB_TOKENS, CORE_COLOR_ROLES, RECOMMENDED_TOKENS, EXAMPLES } from '../spec-config.js'
-import { frontmatterExample, colorsExample, typographyExample, componentsExample, typographyPropertyList, sectionOrderList, componentSubTokenList, recommendedTokens } from './renderers.js'
+import { SPEC_VERSION, SECTIONS, TYPOGRAPHY_PROPERTIES, COMPONENT_SUB_TOKENS, CORE_COLOR_ROLES, RECOMMENDED_TOKENS, EXAMPLES } from '../spec-config.js'
+import { frontmatterExample, colorsExample, typographyExample, componentsExample, typographyPropertyList, typeDefinitions, sectionOrderList, componentSubTokenList, recommendedTokens } from './renderers.js'
 
 # DESIGN.md Format
 
@@ -43,22 +43,10 @@ components:
 
 The `<scale-level>` placeholder represents a named level in a sizing or spacing scale. Common level names include `xs`, `sm`, `md`, `lg`, `xl`, and `full`. Any descriptive string key is valid.
 
-**Color**: A color value is any valid CSS color string. Supported formats include:
-
-- Hex: `#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`
-- Named colors: `red`, `cornflowerblue`, `transparent`
-- Functional: `rgb()`, `rgba()`, `hsl()`, `hsla()`, `hwb()`
-- Wide-gamut: `oklch()`, `oklab()`, `lch()`, `lab()`
-- Mixing: `color-mix(in srgb, ...)`
-
-All color values are internally converted to sRGB for WCAG contrast checking. The original format is preserved for display and export.
-
-Hex notation (`#RRGGBB`) remains the recommended default for simplicity and broad tooling support.
+{typeDefinitions()}
 
 {typographyPropertyList()}
 
-**Dimension**: A dimension value is a string with a unit suffix. Valid units are: {STANDARD_UNITS.join(', ')}.
-
 **Token References**: A token reference must be wrapped in curly braces, and contain an object path to another value in the YAML tree. For most token groups, the reference must point to a primitive value (e.g., `colors.primary-60`), not a group (e.g., `colors`). Within the `components` section, references to composite values (e.g., `{typography.label-md}`) are permitted.
 
 # Sections