# patterns

Design pattern index for the Langroid multi-agent framework. Guides agents on tool handling, task lifecycle control, and external MCP setups.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 2021
- Author: pchalasani
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/pchalasani/claude-code-tools/tree/HEAD/plugins/langroid/skills/patterns/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/patterns

## What it does

This skill acts as a curated index of architectural patterns for building multi-agent setups in Langroid. It organizes design patterns into four categories: core agent tasks, stateful tool handlers, task control rules, and external integrations.

Inside are references to code implementations covering direct `ToolMessage` returns, stateful handlers tracking API retries, and output validation using `AgentDoneTool`. It also provides blueprints for parallel execution using `run_batch_tasks()` with fresh message histories, as well as console cleanup via the `quiet_mode()` manager. Another section details connecting stdio-based MCP servers using the `@mcp_tool` decorator or `get_tools_async()`.

The patterns rely strictly on Langroid constructs such as `TaskConfig` and `DoneTool`. Without the Langroid library in your environment, these blueprints have no target implementation.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add pchalasani/claude-code-tools --skill patterns -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/patterns/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/patterns/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add pchalasani/claude-code-tools --skill patterns -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/patterns/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add pchalasani/claude-code-tools --skill patterns -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/patterns/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install pchalasani/claude-code-tools patterns
```

2. **Manually: put the files in place**
- File: `.github/skills/patterns/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add pchalasani/claude-code-tools --skill patterns -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/pchalasani/claude-code-tools --path plugins/langroid/skills/patterns
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/patterns/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add pchalasani/claude-code-tools --skill patterns -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/pchalasani/claude-code-tools/tree/HEAD/plugins/langroid/skills/patterns/SKILL.md

## When to use it
- validate agent tool outputs against context before task completion
- run concurrent multi-agent batch tasks with state isolation
- connect external MCP tools to Langroid agents via stdio
- mute agent streaming logs during workflow execution

## Example prompts
- Show the Langroid pattern for stateful tool handlers with retry counters
- How do I terminate a Langroid task only when a specific tool runs?
- Give me an example of connecting Claude Code MCP tools to a Langroid agent

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 1729f53ed2f5bf65.

BEGIN THIRD-PARTY FILE 1729f53ed2f5bf65
```text
---
name: patterns
description: Design patterns for the Langroid multi-agent LLM framework. Covers
  agent configuration, tools, task control, and integrations.
---

# 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.

---

## 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`

---

## 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**

   Validate tool output against agent state before accepting it. Use this
   pattern when: (a) the LLM's tool output must preserve certain content from
   the input (e.g., placeholders, required fields), (b) you want automatic
   retry if validation fails, (c) you need to compare tool output against
   context the LLM received. Define a handler method on a custom agent class
   that stores the input context as state, validates the tool output, and
   returns an error string for retry or AgentDoneTool for success (note: use
   AgentDoneTool, NOT DoneTool). Use `done_sequences=["T[ToolName], A"]` so the
   handler runs before task termination.

   - Reference: `./agent-handler-validation-with-state.md`

---

## Task Control

4. **Terminate on Specific Tool**

   Terminate a Task only when a SPECIFIC tool is called. Use
   `TaskConfig(done_sequences=["T[ToolName]"])` to exit immediately when that
   tool is emitted, or `TaskConfig(done_sequences=["T[ToolName], A"])` to exit
   after the tool is emitted AND handled by the agent. Use this when an agent
   has multiple tools but you only want one specific tool to trigger task
   termination.

   - Reference: `./done-sequences-specific-tool.md`

5. **Batch Processing**
```
END THIRD-PARTY FILE 1729f53ed2f5bf65

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---
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