Langroid Patterns

Instructions

Below is an INDEX of design patterns organized by category. Each item describes WHAT you might want to implement, followed by a REFERENCE to a document with a complete code example.

Scan this index to find patterns matching your needs, then consult the corresponding document.

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Agent & Task Basics

1. Task Returns Tool Directly

   Create a Langroid Agent equipped with a single Tool (a ToolMessage), and wrap it in a Task so that running the task returns that ToolMessage directly. Use this pattern when you want a simple LLM agent that returns a structured response.

   • Reference: ./task-return-tool.md

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Tool Handlers

2. Stateful Handler on Agent

   Define a STATEFUL tool handler as a METHOD on the agent (not inside the ToolMessage). Use this pattern when: (a) the tool handler needs to execute external operations (API calls, database queries, file I/O), (b) you need to track state across retries (e.g., failure counter), (c) the handler needs access to agent-level resources (connections, configs), or (d) you want Langroid to automatically loop errors back to the LLM for self-correction. The method name must match the request field of the ToolMessage. Return a string for errors (LLM sees it and can retry), or DoneTool(content=result) to terminate successfully.

   • Reference: ./agent-tool-handler-with-state.md

3. Handler with Validation