GitHub Copilot Custom Skills

This document explains the custom GitHub Copilot skill created for LangChain agent development in this project.

Overview

GitHub Copilot supports custom skills - project-specific knowledge files that help Copilot understand domain patterns, conventions, and workflows. When you ask Copilot questions matching a skill's description, it automatically loads the skill content as context.

What We Added

Skill: langchain-agent-development

Directory Structure

.github/skills/langchain-agent-development/
├── SKILL.md                              # Main skill file (required)
└── checklists/
    ├── new_tool_checklist.md             # Step-by-step for adding tools
    └── add_semantic_route_checklist.md   # Step-by-step for adding routes

File Descriptions

Skill File Format

Required Structure

Every skill must have a SKILL.md file with YAML frontmatter:

---
name: skill-name-here
description: Description of when to use this skill (max 1024 chars)
---

# Skill Title

Content here...

Frontmatter Rules

Our Skill's Frontmatter

---
name: langchain-agent-development
description: Build LangChain ReAct agents with tools, caching, and semantic routing for this stock investment assistant. Use for creating new tools, extending agent capabilities, adding semantic routes, debugging LangGraph issues, and following project patterns (CachingTool, ToolRegistry, AgentResponse).
---

How to Create New Skills

Step 1: Create Directory

mkdir .github/skills/<skill-name>

Step 2: Create SKILL.md

Create .github/skills/<skill-name>/SKILL.md with:

---
name: my-skill-name
description: When to use this skill - be specific about triggers
---

# My Skill

## Overview
What this skill covers...

## Patterns
Code patterns, conventions...

## Quick Reference
Common lookups...

Step 3: Add Supporting Files (Optional)

Add checklists, examples, or templates in subdirectories:

.github/skills/my-skill/
├── SKILL.md
├── checklists/
│   └── workflow_checklist.md
└── examples/
    └── example_code.py

Step 4: Reference in Main Skill

Link to supporting files from SKILL.md:

## Checklists
- [Workflow Checklist](checklists/workflow_checklist.md)

How to Use Skills

Automatic Triggering

Copilot automatically loads skills when your question matches the skill description. For our skill, these queries trigger it:

• "How do I create a new LangChain tool?"
• "Add a semantic route for portfolio analysis"
• "Debug my agent's tool execution"
• "What's the CachingTool pattern in this project?"

Manual Invocation

You can explicitly reference the skill in Copilot Chat:

@workspace Use the langchain-agent-development skill to help me create a new tool

Or reference the skill file directly:

@workspace #file:.github/skills/langchain-agent-development/SKILL.md How do I add caching?

Verification

To verify Copilot loaded the skill, check if responses include:

• Project-specific patterns (CachingTool, ToolRegistry, AgentResponse)
• File paths from your project (src/core/tools/base.py)
• Pattern names from the skill content

Skill Content Summary

Our langchain-agent-development skill covers:

1. Creating New Tools

• Extending CachingTool base class
• Implementing _execute() method
• Registering with ToolRegistry
• Testing patterns

2. Agent Configuration

• ReAct agent setup with create_react_agent
• System prompt patterns
• AgentExecutor configuration

3. Semantic Routing

• StockQueryRoute enum values
• Adding utterances for training
• Router configuration

4. Response Types

• AgentResponse frozen dataclass
• Success, error, and fallback patterns

5. LangGraph Studio Integration

• langgraph.json configuration
• Debugging with Studio
• Tracing execution

6. Troubleshooting

• Common issues table
• Debug checklist

Updating the Skill

When to Update

Update the skill when:

• Adding new tool patterns
• Changing agent architecture
• Adding new route categories
• Discovering common debugging issues

How to Update

1. Edit .github/skills/langchain-agent-development/SKILL.md
2. Update the "Last Updated" date at bottom
3. Increment version if significant changes
4. Add new checklists to checklists/ directory if needed

Version History

References

• Skill Location: .github/skills/langchain-agent-development/SKILL.md
• Tool Checklist: new_tool_checklist.md
• Route Checklist: add_semantic_route_checklist.md
• Backend Instructions: backend-python.instructions.md
• VS Code Copilot Docs: Custom Instructions