Dart schemas for apps & structured AI
Define the shape once. Guide structured AI output, validate every response at runtime, decode wire values into Dart, and generate types when you want them.
final userSchema = Ack.object({
'name': Ack.string().minLength(2),
'email': Ack.string().email(),
'age': Ack.integer().min(0).optional(),
});
final result = userSchema.safeParse({
'name': 'Ada',
'email': 'not-an-email',
});#/emailSchemaError Value must be a valid email address.The same schema follows your data through the entire boundary. Each step is explicit, inspectable, and close to the Dart code—or generated output—that consumes it.
Compose small schemas into the exact object your application accepts. Constraints stay beside the fields they protect.
Explore schemasfinal userSchema = Ack.object({
'name': Ack.string().minLength(2),
'email': Ack.string().email(),
'createdAt': Ack.datetime(),
});Use safeParse at an API, form, storage, or AI boundary. The result makes success and failure deliberate—without a required try/catch.
final result = userSchema
.safeParse(request.body);
if (result.isFail) {
logger.warn(result.getError());
}Object?safeParse()SchemaResultConsume the validated value or route a structured error. Every failure preserves the path and reason your UI, logs, or API response needs.
Work with SchemaResultresult.getOrThrow()Only the shape you described moves forward.
result.getError()#/email pinpoints the invalid field.
Use one Ack schema to guide generation, verify model output, recover rich Dart values, and adapt the contract to the provider you use.
The shipped Firebase AI adapter turns your Ack schema into responseJsonSchema. After generation, the same schema remains the authoritative runtime validator and codec boundary.
final responseSchema = Ack.object({
'answer': Ack.string(),
'sources': Ack.list(Ack.uri()),
'generatedAt': Ack.datetime(),
});
final config = GenerationConfig(
responseJsonSchema:
responseSchema.toFirebaseAiResponseJsonSchema(),
);
final output = responseSchema.parse(
jsonDecode(response.text!),
);AckSchemaModel is the target-independent adapter boundary. Use the built-in toJsonSchema() path, the Firebase AI adapter, or author a focused adapter for OpenAI and other provider SDKs.
AckSchemaModelAnnotate the schema you already trust. Ack generates a lightweight wrapper with typed getters and parse helpers—without changing the runtime schema.
Generate typed schemas@AckType()
final userSchema = Ack.object(...);
final ada = UserType.parse(json);
print(ada.email); // StringAI providers exchange JSON strings. Ack.datetime() validates that wire value, decodes it to UTC DateTime, and encodes it back for the next boundary.
Ack.datetime()VALIDATE · DECODE · ENCODE"2026-07-15T12:00:00Z"DateTime.utc(2026, 7, 15, 12)Add Ack, describe the shape you expect, and keep the rest of your Dart code focused on trusted values.
dart pub add ack