Cursor adds custom tools and nested subagents to TypeScript and Python SDKs
TL;DR
Cursor updated its TypeScript and Python SDKs to support custom tools via local.customTools, auto-review routing, JSONL and custom metadata stores, and infinitely nested subagents.
What changed
Developers gain access to extended Cursor agent capabilities through updates in the TypeScript and Python SDKs that add custom tools via local.customTools and support for infinitely nested subagents. The releases also bring auto-review routing along with JSONL and custom metadata stores. Vibe Builders and Basic Users benefit from these SDK improvements showing up as more adaptable agent behaviors inside Cursor.
Why it matters
Developers working on layered agent workflows now handle custom integrations more directly which aligns with specific use cases like multi-step code review pipelines. This setup gives Vibe Builders clearer paths to organize agent interactions without extra overhead compared to frameworks such as those from LangChain.
What to watch for
Basic Users should compare the new nesting features against alternatives like standard OpenAI Assistants when scaling simple tasks. Developers can verify the updates by reviewing example code in the Cursor changelog and testing a basic custom tool implementation in the Python SDK.
Who this matters for
- Vibe Builders: Use nested subagents to organize complex workflows into manageable, specialized agent tasks.
- Developers: Implement local.customTools in the Python or TS SDK to connect Cursor agents to your private APIs.
Harsh’s take
Cursor is moving fast to absorb the agentic orchestration layer that previously required external frameworks. By adding infinitely nested subagents and custom tool support directly into the SDK, they are making it harder to justify using LangChain or CrewAI for coding tasks. This is a vertical integration play: keep the developer inside the IDE by providing the primitives for complex, multi-step logic.
The addition of JSONL and custom metadata stores suggests Cursor is preparing for more sophisticated RAG and long-term memory features. Operators should stop looking for third-party agent wrappers and start building custom tools that plug directly into this ecosystem. The friction of context switching is the enemy, and Cursor is effectively killing it by letting you script the agent behavior without leaving your workspace.
by Harsh Desai
About Cursor
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