Hanzo Kotlin API Library

The Hanzo Kotlin SDK provides convenient access to the Hanzo REST API from applications written in Kotlin.

The Hanzo Kotlin SDK is similar to the Hanzo Java SDK but with minor differences that make it more ergonomic for use in Kotlin, such as nullable values instead of Optional, Sequence instead of Stream, and suspend functions instead of CompletableFuture.

It is generated with Stainless.

MCP Server

Use the Hanzo MCP Server to enable AI assistants to interact with this API, allowing them to explore endpoints, make test requests, and use documentation to help integrate this SDK into your application.

Note: You may need to set environment variables in your MCP client.

The REST API documentation can be found on docs.hanzo.ai. KDocs are available on javadoc.io.

Installation

Gradle

implementation("ai.hanzo.api:hanzo-kotlin:0.1.0-alpha.2")

Maven

<dependency>
  <groupId>ai.hanzo.api</groupId>
  <artifactId>hanzo-kotlin</artifactId>
  <version>0.1.0-alpha.2</version>
</dependency>

Requirements

This library requires Java 8 or later.

Usage

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient
import ai.hanzo.api.models.ClientGetHomeParams
import ai.hanzo.api.models.ClientGetHomeResponse

// Configures using the `hanzo.apiKey` and `hanzo.baseUrl` system properties
// Or configures using the `HANZO_API_KEY` and `HANZO_BASE_URL` environment variables
val client: HanzoClient = HanzoOkHttpClient.fromEnv()

val response: ClientGetHomeResponse = client.getHome()

Client configuration

Configure the client using system properties or environment variables:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

// Configures using the `hanzo.apiKey` and `hanzo.baseUrl` system properties
// Or configures using the `HANZO_API_KEY` and `HANZO_BASE_URL` environment variables
val client: HanzoClient = HanzoOkHttpClient.fromEnv()

Or manually:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    .apiKey("My API Key")
    .build()

Or using a combination of the two approaches:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    // Configures using the `hanzo.apiKey` and `hanzo.baseUrl` system properties
    // Or configures using the `HANZO_API_KEY` and `HANZO_BASE_URL` environment variables
    .fromEnv()
    .apiKey("My API Key")
    .build()

See this table for the available options:

Setter	System property	Environment variable	Required	Default value
`apiKey`	`hanzo.apiKey`	`HANZO_API_KEY`	true	-
`baseUrl`	`hanzo.baseUrl`	`HANZO_BASE_URL`	true	`"https://api.hanzo.ai"`

System properties take precedence over environment variables.

Tip

Don't create more than one client in the same application. Each client has a connection pool and thread pools, which are more efficient to share between requests.

Modifying configuration

To temporarily use a modified client configuration, while reusing the same connection and thread pools, call withOptions() on any client or service:

import ai.hanzo.api.client.HanzoClient

val clientWithOptions: HanzoClient = client.withOptions {
    it.baseUrl("https://example.com")
    it.maxRetries(42)
}

The withOptions() method does not affect the original client or service.

Requests and responses

To send a request to the Hanzo API, build an instance of some Params class and pass it to the corresponding client method. When the response is received, it will be deserialized into an instance of a Kotlin class.

For example, client.getHome(...) should be called with an instance of ClientGetHomeParams, and it will return an instance of ClientGetHomeResponse.

Immutability

Each class in the SDK has an associated builder or factory method for constructing it.

Each class is immutable once constructed. If the class has an associated builder, then it has a toBuilder() method, which can be used to convert it back to a builder for making a modified copy.

Because each class is immutable, builder modification will never affect already built class instances.

Asynchronous execution

The default client is synchronous. To switch to asynchronous execution, call the async() method:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient
import ai.hanzo.api.models.ClientGetHomeParams
import ai.hanzo.api.models.ClientGetHomeResponse

// Configures using the `hanzo.apiKey` and `hanzo.baseUrl` system properties
// Or configures using the `HANZO_API_KEY` and `HANZO_BASE_URL` environment variables
val client: HanzoClient = HanzoOkHttpClient.fromEnv()

val response: ClientGetHomeResponse = client.async().getHome()

Or create an asynchronous client from the beginning:

import ai.hanzo.api.client.HanzoClientAsync
import ai.hanzo.api.client.okhttp.HanzoOkHttpClientAsync
import ai.hanzo.api.models.ClientGetHomeParams
import ai.hanzo.api.models.ClientGetHomeResponse

// Configures using the `hanzo.apiKey` and `hanzo.baseUrl` system properties
// Or configures using the `HANZO_API_KEY` and `HANZO_BASE_URL` environment variables
val client: HanzoClientAsync = HanzoOkHttpClientAsync.fromEnv()

val response: ClientGetHomeResponse = client.getHome()

The asynchronous client supports the same options as the synchronous one, except most methods are suspending.

File uploads

The SDK defines methods that accept files.

To upload a file, pass a Path:

import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateParams
import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateResponse
import java.nio.file.Paths

val params: TranscriptionCreateParams = TranscriptionCreateParams.builder()
    .file(Paths.get("/path/to/file"))
    .build()
val transcription: TranscriptionCreateResponse = client.audio().transcriptions().create(params)

Or an arbitrary InputStream:

import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateParams
import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateResponse
import java.net.URL

val params: TranscriptionCreateParams = TranscriptionCreateParams.builder()
    .file(URL("https://example.com//path/to/file").openStream())
    .build()
val transcription: TranscriptionCreateResponse = client.audio().transcriptions().create(params)

Or a ByteArray:

import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateParams
import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateResponse

val params: TranscriptionCreateParams = TranscriptionCreateParams.builder()
    .file("content".toByteArray())
    .build()
val transcription: TranscriptionCreateResponse = client.audio().transcriptions().create(params)

Note that when passing a non-Path its filename is unknown so it will not be included in the request. To manually set a filename, pass a MultipartField:

import ai.hanzo.api.core.MultipartField
import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateParams
import ai.hanzo.api.models.audio.transcriptions.TranscriptionCreateResponse
import java.io.InputStream
import java.net.URL

val params: TranscriptionCreateParams = TranscriptionCreateParams.builder()
    .file(MultipartField.builder<InputStream>()
        .value(URL("https://example.com//path/to/file").openStream())
        .filename("/path/to/file")
        .build())
    .build()
val transcription: TranscriptionCreateResponse = client.audio().transcriptions().create(params)

Raw responses

The SDK defines methods that deserialize responses into instances of Kotlin classes. However, these methods don't provide access to the response headers, status code, or the raw response body.

To access this data, prefix any HTTP method call on a client or service with withRawResponse():

import ai.hanzo.api.core.http.Headers
import ai.hanzo.api.core.http.HttpResponseFor
import ai.hanzo.api.models.ClientGetHomeParams
import ai.hanzo.api.models.ClientGetHomeResponse

val response: HttpResponseFor<ClientGetHomeResponse> = client.withRawResponse().getHome()

val statusCode: Int = response.statusCode()
val headers: Headers = response.headers()

You can still deserialize the response into an instance of a Kotlin class if needed:

import ai.hanzo.api.models.ClientGetHomeResponse

val parsedResponse: ClientGetHomeResponse = response.parse()

Error handling

The SDK throws custom unchecked exception types:

HanzoServiceException: Base class for HTTP errors. See this table for which exception subclass is thrown for each HTTP status code:

Status	Exception
400	`BadRequestException`
401	`UnauthorizedException`
403	`PermissionDeniedException`
404	`NotFoundException`
422	`UnprocessableEntityException`
429	`RateLimitException`
5xx	`InternalServerException`
others	`UnexpectedStatusCodeException`

HanzoIoException: I/O networking errors.
HanzoRetryableException: Generic error indicating a failure that could be retried by the client.
HanzoInvalidDataException: Failure to interpret successfully parsed data. For example, when accessing a property that's supposed to be required, but the API unexpectedly omitted it from the response.
HanzoException: Base class for all exceptions. Most errors will result in one of the previously mentioned ones, but completely generic errors may be thrown using the base class.

Logging

The SDK uses the standard OkHttp logging interceptor.

Enable logging by setting the HANZO_LOG environment variable to info:

export HANZO_LOG=info

Or to debug for more verbose logging:

export HANZO_LOG=debug

ProGuard and R8

Although the SDK uses reflection, it is still usable with ProGuard and R8 because hanzo-kotlin-core is published with a configuration file containing keep rules.

ProGuard and R8 should automatically detect and use the published rules, but you can also manually copy the keep rules if necessary.

Jackson

The SDK depends on Jackson for JSON serialization/deserialization. It is compatible with version 2.13.4 or higher, but depends on version 2.18.2 by default.

The SDK throws an exception if it detects an incompatible Jackson version at runtime (e.g. if the default version was overridden in your Maven or Gradle config).

If the SDK threw an exception, but you're certain the version is compatible, then disable the version check using the checkJacksonVersionCompatibility on HanzoOkHttpClient or HanzoOkHttpClientAsync.

Caution

We make no guarantee that the SDK works correctly when the Jackson version check is disabled.

Also note that there are bugs in older Jackson versions that can affect the SDK. We don't work around all Jackson bugs (example) and expect users to upgrade Jackson for those instead.

Network options

Retries

The SDK automatically retries 2 times by default, with a short exponential backoff between requests.

Only the following error types are retried:

Connection errors (for example, due to a network connectivity problem)
408 Request Timeout
409 Conflict
429 Rate Limit
5xx Internal

The API may also explicitly instruct the SDK to retry or not retry a request.

To set a custom number of retries, configure the client using the maxRetries method:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    .maxRetries(4)
    .build()

Timeouts

Requests time out after 1 minute by default.

To set a custom timeout, configure the method call using the timeout method:

import ai.hanzo.api.models.ClientGetHomeResponse

val response: ClientGetHomeResponse = client.getHome(RequestOptions.builder().timeout(Duration.ofSeconds(30)).build())

Or configure the default for all method calls at the client level:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient
import java.time.Duration

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    .timeout(Duration.ofSeconds(30))
    .build()

Proxies

To route requests through a proxy, configure the client using the proxy method:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient
import java.net.InetSocketAddress
import java.net.Proxy

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    .proxy(Proxy(
      Proxy.Type.HTTP, InetSocketAddress(
        "https://example.com", 8080
      )
    ))
    .build()

HTTPS

Note

Most applications should not call these methods, and instead use the system defaults. The defaults include special optimizations that can be lost if the implementations are modified.

To configure how HTTPS connections are secured, configure the client using the sslSocketFactory, trustManager, and hostnameVerifier methods:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    // If `sslSocketFactory` is set, then `trustManager` must be set, and vice versa.
    .sslSocketFactory(yourSSLSocketFactory)
    .trustManager(yourTrustManager)
    .hostnameVerifier(yourHostnameVerifier)
    .build()

Environments

The SDK sends requests to the production by default. To send requests to a different environment, configure the client like so:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    .sandbox()
    .build()

Custom HTTP client

The SDK consists of three artifacts:

hanzo-kotlin-core
- Contains core SDK logic
- Does not depend on OkHttp
- Exposes HanzoClient, HanzoClientAsync, HanzoClientImpl, and HanzoClientAsyncImpl, all of which can work with any HTTP client
hanzo-kotlin-client-okhttp
- Depends on OkHttp
- Exposes HanzoOkHttpClient and HanzoOkHttpClientAsync, which provide a way to construct HanzoClientImpl and HanzoClientAsyncImpl, respectively, using OkHttp
hanzo-kotlin
- Depends on and exposes the APIs of both hanzo-kotlin-core and hanzo-kotlin-client-okhttp
- Does not have its own logic

This structure allows replacing the SDK's default HTTP client without pulling in unnecessary dependencies.

Customized `OkHttpClient`

Tip

Try the available network options before replacing the default client.

To use a customized OkHttpClient:

Replace your hanzo-kotlin dependency with hanzo-kotlin-core
Copy hanzo-kotlin-client-okhttp's OkHttpClient class into your code and customize it
Construct HanzoClientImpl or HanzoClientAsyncImpl, similarly to HanzoOkHttpClient or HanzoOkHttpClientAsync, using your customized client

Completely custom HTTP client

To use a completely custom HTTP client:

Replace your hanzo-kotlin dependency with hanzo-kotlin-core
Write a class that implements the HttpClient interface
Construct HanzoClientImpl or HanzoClientAsyncImpl, similarly to HanzoOkHttpClient or HanzoOkHttpClientAsync, using your new client class

Undocumented API functionality

The SDK is typed for convenient usage of the documented API. However, it also supports working with undocumented or not yet supported parts of the API.

Parameters

To set undocumented parameters, call the putAdditionalHeader, putAdditionalQueryParam, or putAdditionalBodyProperty methods on any Params class:

import ai.hanzo.api.core.JsonValue
import ai.hanzo.api.models.ClientGetHomeParams

val params: ClientGetHomeParams = ClientGetHomeParams.builder()
    .putAdditionalHeader("Secret-Header", "42")
    .putAdditionalQueryParam("secret_query_param", "42")
    .putAdditionalBodyProperty("secretProperty", JsonValue.from("42"))
    .build()

These can be accessed on the built object later using the _additionalHeaders(), _additionalQueryParams(), and _additionalBodyProperties() methods.

To set undocumented parameters on nested headers, query params, or body classes, call the putAdditionalProperty method on the nested class:

import ai.hanzo.api.core.JsonValue
import ai.hanzo.api.models.model.ModelCreateParams

val params: ModelCreateParams = ModelCreateParams.builder()
    .litellmParams(ModelCreateParams.LitellmParams.builder()
        .putAdditionalProperty("secretProperty", JsonValue.from("42"))
        .build())
    .build()

These properties can be accessed on the nested built object later using the _additionalProperties() method.

To set a documented parameter or property to an undocumented or not yet supported value, pass a JsonValue object to its setter:

import ai.hanzo.api.models.ClientGetHomeParams

val params: ClientGetHomeParams = ClientGetHomeParams.builder().build()

The most straightforward way to create a JsonValue is using its from(...) method:

import ai.hanzo.api.core.JsonValue

// Create primitive JSON values
val nullValue: JsonValue = JsonValue.from(null)
val booleanValue: JsonValue = JsonValue.from(true)
val numberValue: JsonValue = JsonValue.from(42)
val stringValue: JsonValue = JsonValue.from("Hello World!")

// Create a JSON array value equivalent to `["Hello", "World"]`
val arrayValue: JsonValue = JsonValue.from(listOf(
  "Hello", "World"
))

// Create a JSON object value equivalent to `{ "a": 1, "b": 2 }`
val objectValue: JsonValue = JsonValue.from(mapOf(
  "a" to 1, "b" to 2
))

// Create an arbitrarily nested JSON equivalent to:
// {
//   "a": [1, 2],
//   "b": [3, 4]
// }
val complexValue: JsonValue = JsonValue.from(mapOf(
  "a" to listOf(
    1, 2
  ), "b" to listOf(
    3, 4
  )
))

Normally a Builder class's build method will throw IllegalStateException if any required parameter or property is unset.

To forcibly omit a required parameter or property, pass JsonMissing:

import ai.hanzo.api.core.JsonMissing
import ai.hanzo.api.models.ClientGetHomeParams
import ai.hanzo.api.models.openai.OpenAICreateParams

val params: ClientGetHomeParams = OpenAICreateParams.builder()
    .endpoint(JsonMissing.of())
    .build()

Response properties

To access undocumented response properties, call the _additionalProperties() method:

import ai.hanzo.api.core.JsonBoolean
import ai.hanzo.api.core.JsonNull
import ai.hanzo.api.core.JsonNumber
import ai.hanzo.api.core.JsonValue

val additionalProperties: Map<String, JsonValue> = client.utils().tokenCounter(params)._additionalProperties()
val secretPropertyValue: JsonValue = additionalProperties.get("secretProperty")

val result = when (secretPropertyValue) {
    is JsonNull -> "It's null!"
    is JsonBoolean -> "It's a boolean!"
    is JsonNumber -> "It's a number!"
    // Other types include `JsonMissing`, `JsonString`, `JsonArray`, and `JsonObject`
    else -> "It's something else!"
}

To access a property's raw JSON value, which may be undocumented, call its _ prefixed method:

import ai.hanzo.api.core.JsonField

val model: JsonField<String> = client.utils().tokenCounter(params)._model()

if (model.isMissing()) {
  // The property is absent from the JSON response
} else if (model.isNull()) {
  // The property was set to literal null
} else {
  // Check if value was provided as a string
  // Other methods include `asNumber()`, `asBoolean()`, etc.
  val jsonString: String? = model.asString();

  // Try to deserialize into a custom type
  val myObject: MyClass = model.asUnknown()!!.convert(MyClass::class.java)
}

Response validation

In rare cases, the API may return a response that doesn't match the expected type. For example, the SDK may expect a property to contain a String, but the API could return something else.

By default, the SDK will not throw an exception in this case. It will throw HanzoInvalidDataException only if you directly access the property.

If you would prefer to check that the response is completely well-typed upfront, then either call validate():

import ai.hanzo.api.models.utils.UtilTokenCounterResponse

val response: UtilTokenCounterResponse = client.utils().tokenCounter(params).validate()

Or configure the method call to validate the response using the responseValidation method:

import ai.hanzo.api.models.ClientGetHomeResponse

val response: ClientGetHomeResponse = client.getHome(RequestOptions.builder().responseValidation(true).build())

Or configure the default for all method calls at the client level:

import ai.hanzo.api.client.HanzoClient
import ai.hanzo.api.client.okhttp.HanzoOkHttpClient

val client: HanzoClient = HanzoOkHttpClient.builder()
    .fromEnv()
    .responseValidation(true)
    .build()

FAQ

Why don't you use plain `enum` classes?

Kotlin enum classes are not trivially forwards compatible. Using them in the SDK could cause runtime exceptions if the API is updated to respond with a new enum value.

Why do you represent fields using `JsonField<T>` instead of just plain `T`?

Using JsonField<T> enables a few features:

Allowing usage of undocumented API functionality
Lazily validating the API response against the expected shape
Representing absent vs explicitly null values

Why don't you use `data` classes?

It is not backwards compatible to add new fields to a data class and we don't want to introduce a breaking change every time we add a field to a class.

Why don't you use checked exceptions?

Checked exceptions are widely considered a mistake in the Java programming language. In fact, they were omitted from Kotlin for this reason.

Checked exceptions:

Are verbose to handle
Encourage error handling at the wrong level of abstraction, where nothing can be done about the error
Are tedious to propagate due to the function coloring problem
Don't play well with lambdas (also due to the function coloring problem)

Semantic versioning

This package generally follows SemVer conventions, though certain backwards-incompatible changes may be released as minor versions:

Changes to library internals which are technically public but not intended or documented for external use. (Please open a GitHub issue to let us know if you are relying on such internals.)
Changes that we do not expect to impact the vast majority of users in practice.

We take backwards-compatibility seriously and work hard to ensure you can rely on a smooth upgrade experience.

We are keen for your feedback; please open an issue with questions, bugs, or suggestions.

Name		Name	Last commit message	Last commit date
Latest commit History 132 Commits
.devcontainer		.devcontainer
.github/workflows		.github/workflows
bin		bin
buildSrc		buildSrc
gradle/wrapper		gradle/wrapper
hanzo-kotlin-client-okhttp		hanzo-kotlin-client-okhttp
hanzo-kotlin-core		hanzo-kotlin-core
hanzo-kotlin-example		hanzo-kotlin-example
hanzo-kotlin-lib		hanzo-kotlin-lib
hanzo-kotlin-proguard-test		hanzo-kotlin-proguard-test
hanzo-kotlin		hanzo-kotlin
scripts		scripts
.gitignore		.gitignore
.release-please-manifest.json		.release-please-manifest.json
.stats.yml		.stats.yml
CHANGELOG.md		CHANGELOG.md
LICENSE		LICENSE
README.md		README.md
SECURITY.md		SECURITY.md
build.gradle.kts		build.gradle.kts
gradle.properties		gradle.properties
gradlew		gradlew
gradlew.bat		gradlew.bat
release-please-config.json		release-please-config.json
settings.gradle.kts		settings.gradle.kts

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Hanzo Kotlin API Library

MCP Server

Installation

Gradle

Maven

Requirements

Usage

Client configuration

Modifying configuration

Requests and responses

Immutability

Asynchronous execution

File uploads

Raw responses

Error handling

Logging

ProGuard and R8

Jackson

Network options

Retries

Timeouts

Proxies

HTTPS

Environments

Custom HTTP client

Customized OkHttpClient

Completely custom HTTP client

Undocumented API functionality

Parameters

Response properties

Response validation

FAQ

Why don't you use plain enum classes?

Why do you represent fields using JsonField<T> instead of just plain T?

Why don't you use data classes?

Why don't you use checked exceptions?

Semantic versioning

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Customized `OkHttpClient`

Why don't you use plain `enum` classes?

Why do you represent fields using `JsonField<T>` instead of just plain `T`?

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