Zod v4 Schema Validation

TypeScript-first schema validation library with static type inference. This skill covers v4 patterns including the metadata registry system.

Schema Annotations

Zod v4 stores metadata in registries (primarily z.globalRegistry). Use .meta() as the primary API and .describe() as shorthand for description-only cases.

IMPORTANT: Always call .meta()/.describe() last in the method chain. Methods like .min(), .optional(), .extend() return new schema instances, so metadata must be attached at the end.

// ✅ Correct - .meta() at end of chain
z.string().min(1).max(100).meta({ description: "User's full name", label: "Name" })

// ✅ Correct - .describe() shorthand for description only
z.string().email().describe("Primary email address")

// ❌ Wrong - metadata lost because .optional() creates new instance
z.string().meta({ description: "Lost!" }).optional()

Annotating object properties:

const userSchema = z.object({
  email: z.string().email().meta({ 
    description: "Used for login",
    label: "Email Address",
    placeholder: "you@example.com"
  }),
  age: z.number().min(0).describe("User's age in years"),
});

API guidance:

• Use .meta(obj) for structured metadata (title, description, examples, UI hints)
• Use .describe(text) as shorthand when only a description string is needed
• Read .description for backwards compatibility with v3 tooling
• Never mutate .description directly—always use .meta()/.describe() to set

Gotchas

• Metadata chain order: .meta()/.describe() MUST be called last—schema methods return new instances
• Don't mutate .description: Read .description for v3 compatibility, but always set via .meta() or .describe()
• .email(), .uuid(), etc. are top-level: Use z.email() not z.string().email() (latter deprecated)
• z.object() strips unknown keys: Use z.strictObject() to reject unknown keys
• .merge() deprecated: Use .extend() instead

References

• Complete API reference: https://zod.dev/llms.txt
• Schema types: https://zod.dev/api
• Metadata/registries: https://zod.dev/metadata
• JSON Schema conversion: https://zod.dev/json-schema
• v3 → v4 migration: https://zod.dev/v4/changelog