Comparisons / Mastra vs Semantic Kernel
Mastra vs Semantic Kernel: Which Agent Framework to Use?
Mastra is a TypeScript-first framework for building AI agents, from the team behind Gatsby. Semantic Kernel is Microsoft's enterprise SDK for building AI agents. Here is how they compare — paradigm, ecosystem, and the use cases each one is actually built for.
By the numbers
Mastra
22.7k
1.8k
TypeScript
MIT
2024-08-06
Mastra AI
244.0k
Semantic Kernel
27.6k
4.5k
C#
MIT
2023-02-27
Microsoft
GitHub stats as of April 2026. Stars indicate community interest, not necessarily quality or fit for your use case.
| Concept | Mastra | Semantic Kernel |
|---|---|---|
| Agent | `new Agent({ model, instructions, tools })` with automatic tool dispatch | `ChatCompletionAgent` with `Kernel`, instructions, and service config |
| Tools | `createTool({ name, schema, execute })` with Zod validation | — |
| Workflows | `Workflow` class with `.step()`, `.then()`, `.branch()` for orchestration | — |
| RAG | Built-in document syncing, chunking, embedding, and vector search | — |
| Memory | Short-term thread memory + long-term vector memory across sessions | `SemanticTextMemory` with embeddings and vector stores |
| Studio | Mastra Studio: local GUI for testing agents, viewing traces, debugging | — |
| Tools / Plugins | — | `KernelPlugin` with `@kernel_function` decorators, typed parameters |
| Planning | — | `StepwisePlanner`, `HandlebarsPlanner` for multi-step decomposition |
| Orchestration | — | `Kernel.invoke()` with plugin resolution and filter pipeline |
| Multi-Language | — | C#, Python, Java SDKs with shared abstractions |
Mastra vs Semantic Kernel, head to head
Mastra Mastra is a TypeScript-first framework for building AI agents, from the team behind Gatsby.
Semantic Kernel Semantic Kernel is Microsoft's enterprise SDK for building AI agents.
Both wrap the same underlying agent pattern — an LLM call, a tool dispatch, a loop — in different abstractions. The choice between them is mostly about which mental model and ecosystem fits the team you have, not which one is technically more capable.
Pick Mastra if
Pick Mastra if mastra is the best option for TypeScript teams that want a batteries-included agent framework without leaving the Node.js ecosystem. The workflow engine and Studio are genuinely productive. For simple agents or Python teams, the plain approach avoids an unnecessary dependency. Mastra is the right fit when the tradeoffs in its intro line up with how your team actually wants to work day-to-day; Semantic Kernel would force you to translate.
Pick Semantic Kernel if
Pick Semantic Kernel if semantic Kernel earns its complexity in enterprise environments with Azure OpenAI, .NET backends, and existing Microsoft infrastructure. But the core agent pattern — LLM call, tool dispatch, loop — is identical to what you can build in 60 lines of Python. Semantic Kernel is the right fit when the tradeoffs in its intro line up with how your team actually wants to work day-to-day; Mastra would force you to translate.
What both add
Both Mastra and Semantic Kernel pull in a class hierarchy and a dependency tree to wrap what is, at the core, an HTTP POST in a while loop. If your use case is straightforward — one provider, a handful of tools, a single agent — the framework cost may exceed the framework benefit. The lesson below shows the same pattern in ~60 lines without either dependency.
Or build your own in 60 lines
Both Mastra and Semantic Kernel implement the same 8 patterns. An agent is a function. Tools are a dict. The loop is a while loop. The whole thing composes in ~60 lines of Python.
No framework. No dependencies. No opinions. Just the code.
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