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Use enum to restrict a field to a list of allowed values.

​
Basic usage

{
  "type": "object",
  "properties": {
    "priority": { "enum": ["low", "medium", "high"] },
    "status": { "enum": ["open", "in_progress", "closed"] }
  },
  "required": ["priority", "status"],
  "additionalProperties": false
}

from typing import Literal
from pydantic import BaseModel, ConfigDict

class Payload(BaseModel):
    model_config = ConfigDict(extra="forbid")

    priority: Literal["low", "medium", "high"]
    status: Literal["open", "in_progress", "closed"]

import { z } from "zod";

const payloadSchema = z
  .object({
    priority: z.enum(["low", "medium", "high"]),
    status: z.enum(["open", "in_progress", "closed"]),
  })
  .strict();
Use enums for categories and statuses so outputs stay predictable.

​
Mixed-type enums

enum values are not restricted to strings: 
{
  "type": "object",
  "properties": {
    "score": { "enum": [1, 2, 3, "unknown", null] }
  },
  "required": ["score"],
  "additionalProperties": false
}

from typing import Literal
from pydantic import BaseModel, ConfigDict

class Payload(BaseModel):
    model_config = ConfigDict(extra="forbid")

    score: Literal[1, 2, 3, "unknown"] | None

import { z } from "zod";

const payloadSchema = z
  .object({
    score: z.union([
      z.literal(1),
      z.literal(2),
      z.literal(3),
      z.literal("unknown"),
      z.null(),
    ]),
  })
  .strict();
For single-value enums, use const instead.