# ApiGear Documentation

> ApiGear generates native SDKs from stateful API definitions. Define interfaces once using ObjectAPI, then generate production-ready code for C++, Qt, Unreal Engine, or Python.


## blog

Blog

- [Blog](/blog.md): Blog

### ai-meets-api-design-mcp

Connect ApiGear to your AI coding assistant via MCP and generate complete SDKs from API descriptions — right from your editor.

- [AI Meets API Design: MCP-Powered SDK Generation](/blog/ai-meets-api-design-mcp.md): Connect ApiGear to your AI coding assistant via MCP and generate complete SDKs from API descriptions — right from your editor.

### api-surface

Overview of a typical API surface for objects in an IDL.

- [API surface for objects](/blog/api-surface.md): Overview of a typical API surface for objects in an IDL.

### archive

Archive

- [Archive](/blog/archive.md): Archive

### authors

- [Authors](/blog/authors.md)

### tags

- [Tags](/blog/tags.md)
- [One post tagged with "ai"](/blog/tags/ai.md)
- [One post tagged with "android"](/blog/tags/android.md)
- [One post tagged with "api"](/blog/tags/api.md)
- [One post tagged with "code-generation"](/blog/tags/code-generation.md)
- [One post tagged with "idl"](/blog/tags/idl.md)
- [One post tagged with "ipc"](/blog/tags/ipc.md)
- [One post tagged with "java"](/blog/tags/java.md)
- [One post tagged with "jni"](/blog/tags/jni.md)
- [One post tagged with "mcp"](/blog/tags/mcp.md)
- [One post tagged with "sdk"](/blog/tags/sdk.md)
- [One post tagged with "unreal"](/blog/tags/unreal.md)

### unreal-android-jni-bridge

Generate the Android Messenger plumbing, Parcelable payloads, and JNI bindings for an Unreal Engine app from one API definition — using the Java and Unreal Engine templates together.

- [ApiGear on Android: Bridging Unreal Engine and Java with Generated JNI](/blog/unreal-android-jni-bridge.md): Generate the Android Messenger plumbing, Parcelable payloads, and JNI bindings for an Unreal Engine app from one API definition — using the Java and Unreal Engine templates together.

## template-cpp14


### docs

- [Features](/template-cpp14/docs/features.md): Overview of the C++14 template features for the ApiGear code generator: generated interfaces and data types, stub implementations, networking adapters, and traffic monitoring.
- [API Feature](/template-cpp14/docs/features/api.md): How the ApiGear C++14 template generates API code from ObjectAPI definitions — interfaces, structs, and enums for your C++14 SDK.
- [Conan package manager](/template-cpp14/docs/features/conan.md): Package the generated ApiGear C++14 SDK with the Conan C++ package manager for clean dependency management and reuse.
- [Monitor](/template-cpp14/docs/features/monitor.md): Traffic monitoring in the ApiGear C++14 template: trace interface properties, methods, and signals from your C++14 SDK in ApiGear Studio.
- [MQTT](/template-cpp14/docs/features/mqtt.md): MQTT networking in the ApiGear C++14 template: expose and consume C++14 interfaces over MQTT using generated client and server adapters.
- [OLink](/template-cpp14/docs/features/olink.md): OLink (ObjectLink) networking in the ApiGear C++14 template: connect C++14 interface clients and services over the ObjectLink protocol with built-in monitoring.
- [Stubs](/template-cpp14/docs/features/stubs.md): Generated stub implementations in the ApiGear C++14 template: ready-to-extend default classes for your interfaces, ideal for prototyping and testing C++14 services.
- [Template C++ 14 (Maintenance)](/template-cpp14/docs/intro.md): Maintenance-mode C++14 template for the ApiGear code generator. Generate C++14-compatible SDKs with OLink and MQTT networking; new projects should use the C++17 template.
- [Quick-Start](/template-cpp14/docs/quickstart.md): Quick-start guide for the ApiGear C++14 template: install the generator, define an ObjectAPI interface, and generate your first C++14 SDK in minutes.

## template-cpp17


### docs

- [Features](/template-cpp17/docs/features.md): Overview of the C++17 template features for the ApiGear code generator: generated interfaces and data types, stub implementations, networking adapters, and traffic monitoring.
- [API Feature](/template-cpp17/docs/features/api.md): How the ApiGear C++17 template generates API code from ObjectAPI definitions — interfaces, structs, and enums for your C++17 SDK.
- [Conan package manager](/template-cpp17/docs/features/conan.md): Package the generated ApiGear C++17 SDK with the Conan C++ package manager for clean dependency management and reuse.
- [Monitor](/template-cpp17/docs/features/monitor.md): Traffic monitoring in the ApiGear C++17 template: trace interface properties, methods, and signals from your C++17 SDK in ApiGear Studio.
- [MQTT](/template-cpp17/docs/features/mqtt.md): MQTT networking in the ApiGear C++17 template: expose and consume C++17 interfaces over MQTT using generated client and server adapters.
- [NATS](/template-cpp17/docs/features/nats.md): NATS networking in the ApiGear C++17 template: connect C++17 interface clients and services over the NATS messaging system.
- [OLink](/template-cpp17/docs/features/olink.md): OLink (ObjectLink) networking in the ApiGear C++17 template: connect C++17 interface clients and services over the ObjectLink protocol with built-in monitoring.
- [Stubs](/template-cpp17/docs/features/stubs.md): Generated stub implementations in the ApiGear C++17 template: ready-to-extend default classes for your interfaces, ideal for prototyping and testing C++17 services.
- [Template C++ 17](/template-cpp17/docs/intro.md): Generate modern C++17 SDKs from ObjectAPI definitions with ApiGear: interfaces, structs, stub implementations, plus OLink, NATS, and MQTT networking with built-in monitoring.
- [Quick-Start](/template-cpp17/docs/quickstart.md): Quick-start guide for the ApiGear C++17 template: install the generator, define an ObjectAPI interface, and generate your first C++17 SDK in minutes.

## template-java


### docs

- [Features](/template-java/docs/features.md): Overview of ApiGear Java template features: API generation, stub implementations, Android service/client IPC, and JNI bridge.
- [Android Feature](/template-java/docs/features/android.md): Generate Android Messenger-based service/client architecture for cross-process and cross-app API communication.
- [API Feature](/template-java/docs/features/api.md): Generate Java interfaces, structs, enums, and abstract base classes from API definitions. Includes async operations, property change listeners, and ready-state management.
- [JNI Bridge Feature](/template-java/docs/features/jnibridge.md): Generate JNI bridge classes for integrating the Java/Android API with native C++ code, such as Unreal Engine.
- [Stubs](/template-java/docs/features/stubs.md): Generate ready-to-use stub implementations with property change detection, async operations, and ready-state management.
- [Template Java](/template-java/docs/intro.md): Generate Java interfaces, Android service/client IPC, and JNI bridge code from API definitions with the ApiGear code generator.
- [Quick-Start](/template-java/docs/quickstart.md): Step-by-step guide to generate Java interfaces and data types from YAML API definitions using the ApiGear code generator.

## template-python


### docs

- [Features](/template-python/docs/features.md): Overview of the Python template features for the ApiGear code generator: generated interfaces and data types, stub implementations, networking adapters, and traffic monitoring.
- [MQTT](/template-python/docs/features/mqtt.md): MQTT networking in the ApiGear Python template: expose and consume Python interfaces over MQTT using generated client and server adapters.
- [Template Python](/template-python/docs/intro.md): Generate Python SDKs from ObjectAPI definitions with ApiGear: typed interfaces, asyncio clients, OLink and MQTT networking, and monitoring for stateful APIs.
- [Quick-Start](/template-python/docs/quickstart.md): Quick-start guide for the ApiGear Python template: install the generator, define an ObjectAPI interface, and generate your first Python SDK in minutes.

## template-qt6


### docs

- [Features](/template-qt6/docs/features.md): Overview of the Qt6 C++ template features for the ApiGear code generator: generated interfaces and data types, stub implementations, networking adapters, and traffic monitoring.
- [API](/template-qt6/docs/features/api.md): How the ApiGear Qt6 C++ template generates API code from ObjectAPI definitions — interfaces, structs, and enums for your Qt6 C++ SDK.
- [Monitor](/template-qt6/docs/features/monitor.md): Traffic monitoring in the ApiGear Qt6 C++ template: trace interface properties, methods, and signals from your Qt6 C++ SDK in ApiGear Studio.
- [MQTT](/template-qt6/docs/features/mqtt.md): MQTT networking in the ApiGear Qt6 C++ template: expose and consume Qt6 C++ interfaces over MQTT using generated client and server adapters.
- [OLink](/template-qt6/docs/features/olink.md): OLink (ObjectLink) networking in the ApiGear Qt6 C++ template: connect Qt6 C++ interface clients and services over the ObjectLink protocol with built-in monitoring.
- [QML Plugin](/template-qt6/docs/features/qmlplugin.md): Generate a QML plugin from ObjectAPI definitions with the ApiGear Qt6 template — use your interfaces directly in QML and Qt Quick applications.
- [Stubs](/template-qt6/docs/features/stubs.md): Generated stub implementations in the ApiGear Qt6 C++ template: ready-to-extend default classes for your interfaces, ideal for prototyping and testing Qt6 C++ services.
- [Template Qt6](/template-qt6/docs/intro.md): Generate Qt6 C++ and QML SDKs from ObjectAPI definitions with ApiGear: QObject-based interfaces, QML-ready types, OLink and MQTT networking, and built-in monitoring.
- [Quick-Start](/template-qt6/docs/quickstart.md): Quick-start guide for the ApiGear Qt6 C++ template: install the generator, define an ObjectAPI interface, and generate your first Qt6 C++ SDK in minutes.

## template-rust


### docs

- [Features](/template-rust/docs/features.md): Overview of the Rust template features for the ApiGear code generator: generated interfaces and data types, stub implementations, networking adapters, and traffic monitoring.
- [API Feature](/template-rust/docs/features/api.md): How the ApiGear Rust template generates API code from ObjectAPI definitions — interfaces, structs, and enums for your Rust SDK.
- [Monitor](/template-rust/docs/features/monitor.md): Traffic monitoring in the ApiGear Rust template: trace interface properties, methods, and signals from your Rust SDK in ApiGear Studio.
- [MQTT](/template-rust/docs/features/mqtt.md): MQTT networking in the ApiGear Rust template: expose and consume Rust interfaces over MQTT using generated client and server adapters.
- [NATS](/template-rust/docs/features/nats.md): NATS networking in the ApiGear Rust template: connect Rust interface clients and services over the NATS messaging system.
- [OLink](/template-rust/docs/features/olink.md): OLink (ObjectLink) networking in the ApiGear Rust template: connect Rust interface clients and services over the ObjectLink protocol with built-in monitoring.
- [Stubs](/template-rust/docs/features/stubs.md): Generated stub implementations in the ApiGear Rust template: ready-to-extend default classes for your interfaces, ideal for prototyping and testing Rust services.
- [Template Rust](/template-rust/docs/intro.md): Generate Rust SDKs from ObjectAPI definitions with ApiGear: trait-based interfaces, async Tokio clients, OLink, NATS, and MQTT networking, and built-in monitoring.
- [Quick-Start](/template-rust/docs/quickstart.md): Quick-start guide for the ApiGear Rust template: install the generator, define an ObjectAPI interface, and generate your first Rust SDK in minutes.

## template-unreal


### docs

- [Features](/template-unreal/docs/features.md): Overview of ApiGear Unreal Engine template features: Core API generation, stub implementations, OLink networking, MQTT pub/sub, JNI Android communication, Message Bus IPC, and runtime monitoring.
- [API Feature](/template-unreal/docs/features/api.md): Generate Unreal Engine interfaces, structs, and enums from API definitions. Full Blueprint and C++ support with property change notifications and async operations.
- [JNI](/template-unreal/docs/features/jni.md): Connect Unreal Engine to Android services via JNI. Adapter and client for cross-platform Unreal Engine and Android communication using the Java template's jnibridge feature.
- [Licensing and Author Metadata](/template-unreal/docs/features/licensing.md): Generated plugins include MIT LICENSE files and SPDX headers. Customize author metadata in .uplugin descriptors and copyright notices via the meta field.
- [Monitor](/template-unreal/docs/features/monitor.md): Trace API calls, property changes, and signals at runtime. View live debugging data in ApiGear Studio or CLI for Unreal Engine interfaces.
- [MQTT](/template-unreal/docs/features/mqtt.md): Connect Unreal Engine to any MQTT broker. Publish and subscribe to topics for IoT, telemetry, and many-to-many communication with non-Unreal peers.
- [Message Bus](/template-unreal/docs/features/msgbus.md): Use Unreal Engine's built-in Message Bus for IPC between Unreal applications. Zero-config local communication for editor tools and distributed systems.
- [OLink](/template-unreal/docs/features/olink.md): Connect Unreal Engine to remote services via ObjectLink WebSocket protocol. Client and server adapters for cross-platform communication and simulation.
- [Stubs](/template-unreal/docs/features/stubs.md): Generate ready-to-use stub implementations as Unreal Engine GameInstance Subsystems. Includes test fixtures and property change notifications.
- [Template Unreal Engine](/template-unreal/docs/intro.md): Generate Unreal Engine plugins from API definitions with full Blueprint and C++ support. Create production-ready code with OLink networking, Message Bus IPC, and monitoring.
- [Quick-Start](/template-unreal/docs/quickstart.md): Step-by-step guide to generate Unreal Engine plugins from YAML API definitions. Learn to create Blueprint and C++ interfaces with ApiGear code generator.

## docs

ApiGear generates native SDKs from stateful API definitions using ObjectAPI. Generate production-ready code for C++, Qt, Unreal Engine, and Python.

- [Introduction](/docs.md): ApiGear generates native SDKs from stateful API definitions using ObjectAPI. Generate production-ready code for C++, Qt, Unreal Engine, and Python.

### cli

- [Code Generation](/docs/cli/generate.md): Generate SDKs from ObjectAPI definitions using solution files or expert mode. Covers CLI flags, solution file format, features, and error handling.
- [Introduction](/docs/cli/intro.md): Install and use the ApiGear CLI to generate production-ready SDKs, simulate APIs, monitor traffic, and integrate with AI assistants via MCP.
- [MCP Server](/docs/cli/mcp.md): Use the ApiGear MCP server to expose SDK generation, template management, and spec validation as tools for Claude Code, Cursor, and other AI assistants.
- [API Monitoring](/docs/cli/monitor.md): Monitor API traffic in real-time using the ApiGear CLI. View property changes, operation calls, and signals from your generated SDK applications.
- [ObjectLink REPL](/docs/cli/olink.md): Use the ObjectLink REPL to connect to servers, link remote objects, invoke methods, set properties, and observe signals interactively over WebSocket.
- [Project Management](/docs/cli/project.md): Create, edit, and manage ApiGear projects. Set up API modules, solution files, and simulation scenarios from the command line.
- [Scripting Support](/docs/cli/simulate.md): Simulate API backends with JavaScript scripts or YAML scenarios. Test your application against mock data before real services exist.
- [SDK Templates](/docs/cli/template.md): Manage SDK templates for code generation. Install from the registry, list cached templates, and search for available templates.

### guide

- [Calculator API Demo](/docs/guide/calculator.md): Create and simulate a Calculator API in minutes using ApiGear’s model-driven generator.
- [Counter API Demo](/docs/guide/counter.md): Walk through building a coffee counter API with ApiGear. Define an ObjectAPI module, configure a solution, generate code, and simulate the backend.
- [Quick Start](/docs/guide/quick-start.md): Generate your first SDK in 5 minutes. Install ApiGear, define an API module, configure a solution file, and generate C++, Qt, Unreal Engine, or Python code.
- [Update Strategy](/docs/guide/update-strategy.md): Strategies for managing generated code updates when your API evolves. Understand the force flag, protected files, and merge approaches.

### monitor

- [Introduction](/docs/monitor/intro.md): Monitor API usage in real-time during development and testing. Detect anomalies by tracking property changes, operation calls, and signals.
- [Monitoring Protocol](/docs/monitor/protocol.md): The API Monitor protocol uses HTTP POST to report property changes, operation calls, and signals to the embedded monitoring server.

### objectapi

- [Advanced Concepts](/docs/objectapi/advanced.md): Advanced ObjectAPI concepts including document info blocks, meta annotations for custom code generation, and compact YAML writing format.
- [API Foundation](/docs/objectapi/core.md): Learn the ObjectAPI document format, primitive types (bool, int, float, string), arrays, complex types, and cross-module imports.
- [API Examples](/docs/objectapi/examples.md): Complete ObjectAPI YAML examples including a Counter, Radio Tuner with structs and enums, and a Weather Station with signals.
- [ObjectAPI IDL](/docs/objectapi/idl.md): Write APIs using the ObjectAPI IDL, a concise code-like syntax that auto-converts to YAML. Covers modules, interfaces, structs, enums, and imports.
- [Introduction](/docs/objectapi/intro.md): ObjectAPI defines stateful, object-oriented APIs — properties, operations, and signals — and gives designers and engineers a shared language from rapid prototyping to production.
- [API Modules](/docs/objectapi/modules.md): Define API modules with interfaces (properties, operations, signals), data structures, and enumerations using the ObjectAPI specification.

### protocols

- [HTTP Mapping](/docs/protocols/http/mapping_http.md): Map ObjectAPI interfaces to HTTP endpoints using an RPC model. Covers property, operation, and signal mapping with JSON payloads.
- [Protocol Mappings](/docs/protocols/mapping.md): How ApiGear's ObjectAPI relates to OpenAPI, AsyncAPI, gRPC, MQTT, SOME/IP and DDS — and why it generates code that runs over them instead of replacing them.
- [ApiGear over MQTT](/docs/protocols/mqtt/intro.md): How ApiGear maps ObjectAPI interfaces onto MQTT v5: brokered pub/sub for properties, signals and operations, shared across the C++, Qt, Python, Rust and Unreal templates.
- [ApiGear MQTT Topic Mapping](/docs/protocols/mqtt/mapping.md): The ApiGear MQTT v5 topic-mapping spec: how interface operations, signals and properties map to MQTT topics and JSON payloads, with correlation, retained state and a v3 fallback.
- [ApiGear over NATS](/docs/protocols/nats/intro.md): How ApiGear maps ObjectAPI interfaces onto NATS subjects: request/reply for operations, pub/sub for signals and properties, plus connectivity messaging, shared across templates.
- [ApiGear NATS Subject Mapping](/docs/protocols/nats/mapping.md): How ApiGear maps ObjectAPI interface operations, signals and properties onto NATS subjects and JSON payloads, with request/reply and connectivity messaging.
- [Use Cases](/docs/protocols/objectlink/cases.md): ObjectLink use cases including embedded service sharing, sensor-to-dashboard linking, and UI-to-service layer communication across platforms.
- [Error Messages](/docs/protocols/objectlink/errors.md): ObjectLink error message format and error codes. Covers error handling for link, invoke, set-property, and signal operations.
- [Introduction](/docs/protocols/objectlink/intro.md): ObjectLink is an IPC protocol that links local objects to remote objects over network connections, synchronizing properties, operations, and signals.
- [Lifecycle](/docs/protocols/objectlink/lifecycle.md): Manage the ObjectLink object lifecycle with LINK, INIT, and UNLINK messages. Learn how remote objects are linked and initialized with property state.
- [Method Invokation](/docs/protocols/objectlink/methods.md): Invoke methods on remote objects using the ObjectLink protocol. Covers INVOKE and INVOKE_REPLY message format with request IDs.
- [Property Synchronization](/docs/protocols/objectlink/properties.md): Synchronize object properties between local and remote objects. Covers SET_PROPERTY and PROPERTY_CHANGE messages for real-time state updates.
- [Server Side Signals](/docs/protocols/objectlink/signals.md): Receive server-side event notifications through ObjectLink signals. Signals push events from remote objects to all linked local objects.

### scripting

- [JavaScript API](/docs/scripting/backends/api.md): JavaScript API reference for the simulation server. Covers actors, property handling, operation callbacks, signal emission, and timer functions.
- [Simulation Examples](/docs/scripting/backends/examples.md): Complete simulation examples including a heating control system with thermostat logic, a ball physics animation, and a vehicle dashboard with multiple services.
- [Service Simulation](/docs/scripting/backends/intro.md): Simulate API services with JavaScript to test client code without real backends. Create virtual objects with state, behavior, and change notifications.
- [Simulation Protocol](/docs/scripting/backends/protocols.md): How the simulation framework uses the ObjectLink protocol to serve simulated API responses to clients over network connections.
- [Simulation Scenarios](/docs/scripting/backends/scenario.md): Write simulation scenarios in JavaScript to define API endpoint behavior. Configure actors with properties, operation handlers, and signal emitters.
- [Generator Based Simulation](/docs/scripting/backends/solution.md): Auto-generate simulation scenarios from API definitions. Quickly scaffold mock backends for large APIs without writing simulation code by hand.
- [Examples](/docs/scripting/clients/examples.md): JavaScript client script examples that connect to remote services. Includes counter increment and heating system control scenarios.
- [Scripted Clients](/docs/scripting/clients/intro.md): Use JavaScript client scripts to trigger operation sequences and data changes on remote services via the ObjectLink protocol.
- [Scripting](/docs/scripting/intro.md): Use JavaScript scripting to simulate API backends and drive API clients. Test, prototype, and demo without compiled code or deployed services.

### sdk

- [SDK Templates](/docs/sdk/intro.md): Browse available SDK templates for code generation. Includes C++17, Qt 6, Unreal Engine, Python, Go, Rust, and TypeScript with protocol and monitoring support.
- [Filter Reference](/docs/sdk/maker/filters.md): Reference for template filters that transform text in SDK templates. Covers case conversion (snake, camel, pascal), path helpers, and string utilities.
- [Introduction](/docs/sdk/maker/intro.md): Create and customize SDK templates for ApiGear code generation. Adapt existing templates or build new ones for your technology stack.
- [Rules Document](/docs/sdk/maker/rules.md): Define code generation rules with features, file output targets, and template-to-source mappings. Control which files are generated and when.
- [Symbol Reference](/docs/sdk/maker/symbols.md): Reference for all symbols available in SDK templates. Covers System, Module, Interface, Structure, Enumeration, and their properties.
- [Template Primer](/docs/sdk/maker/template.md): Learn the Go text/template syntax used in ApiGear SDK templates. Covers variables, loops, conditionals, functions, and template composition.
- [Quick Start](/docs/sdk/maker/tutorial.md): Step-by-step tutorial to create an SDK template that generates TypeScript interfaces from ObjectAPI definitions. Covers rules, templates, and solution setup.

### studio

- [Introduction](/docs/studio/intro.md): ApiGear Studio is a desktop application for designing APIs, generating SDKs, running simulations, and monitoring API traffic in one integrated environment.
- [Project Management](/docs/studio/project.md): Create, open, and manage API projects in ApiGear Studio. Organize modules, solutions, and scenarios within the project workspace.
- [Quick Start](/docs/studio/quickstart.md): Get started with ApiGear Studio. Create a project, define API modules, configure code generation, and monitor API traffic in the desktop IDE.