code-tour

What this skill does

# Code Tour

Create **CodeTour** files — persona-targeted, step-by-step walkthroughs of a codebase that link directly to files and line numbers. CodeTour files live in `.tours/` and work with the [VS Code CodeTour extension](https://github.com/microsoft/codetour).

## Overview

A great tour is a **narrative** — a story told to a specific person about what matters, why it matters, and what to do next. Only create `.tour` JSON files. Never modify source code.

## When to Use This Skill

- User asks to create a code tour, onboarding tour, or architecture walkthrough
- User says "tour for this PR", "explain how X works", "vibe check", "RCA tour"
- User wants a contributor guide, security review, or bug investigation walkthrough
- Any request for a structured walkthrough with file/line anchors

## Core Workflow

### 1. Discover the repo

Before asking anything, explore the codebase:

In parallel: list root directory, read README, check config files.
Then: identify language(s), framework(s), project purpose. Map folder structure 1-2 levels deep. Find entry points — every path in the tour must be real.

If the repo has fewer than 5 source files, create a quick-depth tour regardless of persona — there's not enough to warrant a deep one.

### 2. Infer the intent

One message should be enough. Infer persona, depth, and focus silently.

| User says | Persona | Depth |
|-----------|---------|-------|
| "tour for this PR" | pr-reviewer | standard |
| "why did X break" / "RCA" | rca-investigator | standard |
| "onboarding" / "new joiner" | new-joiner | standard |
| "quick tour" / "vibe check" | vibecoder | quick |
| "architecture" | architect | deep |
| "security" / "auth review" | security-reviewer | standard |
| (no qualifier) | new-joiner | standard |

When intent is ambiguous, default to **new-joiner** persona at **standard** depth — it's the most generally useful.

### 3. Read actual files

**Every file path and line number must be verified.** A tour pointing to the wrong line is worse than no tour.

### 4. Write the tour

Save to `.tours/<persona>-<focus>.tour`.

```json
{
  "$schema": "https://aka.ms/codetour-schema",
  "title": "Descriptive Title — Persona / Goal",
  "description": "Who this is for and what they'll understand after.",
  "ref": "<current-branch-or-commit>",
  "steps": []
}
```

### Step types

| Type | When to use | Example |
|------|-------------|---------|
| **Content** | Intro/closing only (max 2) | `{ "title": "Welcome", "description": "..." }` |
| **Directory** | Orient to a module | `{ "directory": "src/services", "title": "..." }` |
| **File + line** | The workhorse | `{ "file": "src/auth.ts", "line": 42, "title": "..." }` |
| **Selection** | Highlight a code block | `{ "file": "...", "selection": {...}, "title": "..." }` |
| **Pattern** | Regex match (volatile files) | `{ "file": "...", "pattern": "class App", "title": "..." }` |
| **URI** | Link to PR, issue, doc | `{ "uri": "https://...", "title": "..." }` |

### Step count

| Depth | Steps | Use for |
|-------|-------|---------|
| Quick | 5-8 | Vibecoder, fast exploration |
| Standard | 9-13 | Most personas |
| Deep | 14-18 | Architect, RCA |

### Writing descriptions — SMIG formula

- **S — Situation**: What is the reader looking at?
- **M — Mechanism**: How does this code work?
- **I — Implication**: Why does this matter for this persona?
- **G — Gotcha**: What would a smart person get wrong?

### 5. Validate

- [ ] Every `file` path relative to repo root (no leading `/` or `./`)
- [ ] Every `file` confirmed to exist
- [ ] Every `line` verified by reading the file
- [ ] First step has `file` or `directory` anchor
- [ ] At most 2 content-only steps
- [ ] `nextTour` matches another tour's `title` exactly if set

## Personas

| Persona | Goal | Must cover |
|---------|------|------------|
| **Vibecoder** | Get the vibe fast | Entry point, main modules. Max 8 steps. |
| **New joiner** | Structured ramp-up | Directories, setup, business context |
| **Bug fixer** | Root cause fast | Trigger -> fault points -> tests |
| **RCA investigator** | Why did it fail | Causality chain, observability anchors |
| **Feature explainer** | End-to-end | UI -> API -> backend -> storage |
| **PR reviewer** | Review correctly | Change story, invariants, risky areas |
| **Architect** | Shape and rationale | Boundaries, tradeoffs, extension points |
| **Security reviewer** | Trust boundaries | Auth flow, validation, secret handling |
| **Refactorer** | Safe restructuring | Seams, hidden deps, extraction order |
| **External contributor** | Contribute safely | Safe areas, conventions, landmines |

## Narrative Arc

1. **Orientation** — `file` or `directory` step (never content-only first step — blank in VS Code)
2. **High-level map** — 1-3 directory steps showing major modules
3. **Core path** — file/line steps, the heart of the tour
4. **Closing** — what the reader can now do, suggested follow-ups

## Anti-Patterns

| Anti-pattern | Fix |
|---|---|
| **File listing** — "this file contains the models" | Tell a story. Each step depends on the previous. |
| **Generic descriptions** | Name the specific pattern unique to this codebase. |
| **Line number guessing** | Never write a line you didn't verify by reading. |
| **Too many steps** for quick depth | Actually cut steps. |
| **Hallucinated files** | If it doesn't exist, skip the step. |
| **Recap closing** — "we covered X, Y, Z" | Tell the reader what they can now *do*. |
| **Content-only first step** | Anchor step 1 to a file or directory. |

## Cross-References

- Related: `engineering/codebase-onboarding` — for broader onboarding beyond tours
- Related: `engineering/pr-review-expert` — for automated PR review workflows
- CodeTour extension: [microsoft/codetour](https://github.com/microsoft/codetour)
- Real-world tours: [coder/code-server](https://github.com/coder/code-server/blob/main/.tours/contributing.tour)