# Semantic Kernel review > Semantic Kernel is an open-source middleware SDK by Microsoft that connects AI models to C#, Python, and Java codebases to automate business processes with agents and plugins. - Canonical: https://toolsrankai.com/tools/semantic-kernel - Official site: https://learn.microsoft.com/en-us/semantic-kernel/overview/ - ToolsRank rank / score: #90 / 78.7 (methodology https://toolsrankai.com/methodology) - Categories: AI Agent & Chatbot Builders, Agent Platforms & Frameworks, AI Coding & Development - Pricing: Free & open source. At the review date, Semantic Kernel is an open-source SDK distributed without software license fees. Cloud compute and third-party model inference usage incur separate provider costs. - Fact-checked: 2026-09-08 · First listed: 2026-09-23 ## Verdict Semantic Kernel is an ideal choice for software engineers seeking a stable, multi-language SDK to orchestrate enterprise AI agents and function calling. It is not designed for non-technical users looking for a visual no-code interface. ## What it is Semantic Kernel is an open-source software development kit designed to act as an efficient middleware layer between modern AI models and enterprise application code. Maintained by Microsoft, it enables engineering teams to build modular AI agents and integrate large language models directly into C#, Python, or Java environments. The framework coordinates function calling by translating model prompts and requests into executable code against existing APIs, then returning structured results back to the model. Rather than locking applications into a single vendor or model architecture, it allows developers to swap out underlying AI models as technology advances without refactoring entire application codebases. Semantic Kernel incorporates enterprise features such as telemetry support, execution hooks, and filters to monitor performance and enforce responsible AI boundaries. It also supports OpenAPI specifications, allowing teams to expose existing corporate systems as standardized plugins that can be shared across pro-code developers and low-code environments. **What makes it different:** Semantic Kernel delivers production-ready Version 1.0+ API stability across C#, Python, and Java, combining function calling middleware with native OpenAPI plugin support compatible with Microsoft 365 Copilot. **Best for:** software engineers building enterprise AI agents and function-calling workflows in C#, Python, or Java **Not ideal for:** non-technical users looking for a graphical drag-and-drop agent builder without code deployment ## Key features - **Middleware Function Calling** — Translates language model requests into function calls against existing APIs and feeds execution results back to the model. - **Multi-Language v1.0+ Stability** — Provides committed non-breaking API stability across C#, Python, and Java codebases. - **Model Swapping** — Decouples application logic from specific models, allowing developers to upgrade or change AI providers without rewriting code. - **OpenAPI Plugin Ecosystem** — Packages existing APIs into modular plugins using standard OpenAPI specifications, enabling reuse across enterprise tools. - **Telemetry and Observability** — Includes built-in telemetry, hooks, and filters to monitor agent execution and apply responsible AI safeguards. - **Multimodal Expansion** — Enables existing chat-based endpoints to expand into additional interaction modalities like voice and video. ## Use cases - **Automating API Workflows** — Exposing internal enterprise APIs as plugins so AI models can orchestrate multi-step business transactions. - **Enterprise Agent Orchestration** — Developing reliable AI agents inside existing C#, Python, or Java enterprise systems with logging and filters. - **Cross-Team Extension Sharing** — Standardizing AI skills via OpenAPI so pro-code plugins can be consumed by other teams and copilots. ## Pros - Committed v1.0+ non-breaking API stability across C#, Python, and Java - Open-source development kit with no software licensing fees - Native support for telemetry, security filters, and hooks - OpenAPI standard alignment facilitates plugin reuse ## Limitations - Requires professional software development experience to deploy and maintain - Visual workflow management is not provided in the core SDK ## Pricing At the review date, Semantic Kernel is an open-source SDK distributed without software license fees. Cloud compute and third-party model inference usage incur separate provider costs. Vendor prices and limits change; verify on the official pricing page before purchasing. ## Score factors - editorial: 82 (editorial) - utility: 88 (editorial) - trust: 85 (editorial) - freshness: 78 (editorial) - engagement: 8 (measured) - momentum: 100 (measured) ## Languages, platforms, integrations - Languages: en - Integrations: OpenAPI, Microsoft 365 Copilot, C#, Python, Java ## FAQ ### What programming languages does Semantic Kernel support? Semantic Kernel provides official Version 1.0+ support with non-breaking API commitments for C#, Python, and Java. ### Is Semantic Kernel free to use? Yes. Semantic Kernel is a lightweight, open-source development kit. Users do not pay software license fees for the SDK, though model API calls and hosting infrastructure incur independent costs. ### How does Semantic Kernel connect code to AI models? Semantic Kernel acts as middleware: it describes existing code and APIs to the model, intercepts the model's requested function calls, executes the code, and passes the output back to the model. ### Does Semantic Kernel support plugins from other tools? Yes. Semantic Kernel supports OpenAPI specifications, allowing developers to create plugins that can be shared with other developers or integrated with copilots like Microsoft 365 Copilot. ## Alternatives - [Dify](https://toolsrankai.com/tools/dify) — An open-source LLM app platform with visual workflows, RAG, and agent tooling, available self-hosted or as a cloud service. - [Botpress](https://toolsrankai.com/tools/botpress) — An agent-building platform with a visual studio, hosted runtime, and an open-source lineage. ## Sources checked - [Semantic Kernel Overview](https://learn.microsoft.com/en-us/semantic-kernel/overview/) --- Cite https://toolsrankai.com/tools/semantic-kernel for ToolsRank's editorial judgment; verify changing vendor facts through the sources above. Reviewed 2026-09-08.