# Phase 3: Discovery Endpoints - Implementation Notes

**Date:** October 16, 2025  
**Status:** ✅ Complete  
**Estimated Effort:** 2-3 days  
**Actual Effort:** ~1 hour

---

## Overview

Phase 3 adds two new discovery tools that enable exploring vault structure and testing path validity without performing full operations. These tools are essential for AI agents and scripts to verify paths before attempting operations.

---

## Implementation Summary

### 1. Type Definitions (`src/types/mcp-types.ts`)

Added two new result types:

```typescript
export interface StatResult {
	path: string;
	exists: boolean;
	kind?: ItemKind;
	metadata?: FileMetadata | DirectoryMetadata;
}

export interface ExistsResult {
	path: string;
	exists: boolean;
	kind?: ItemKind;
}
```

### 2. VaultTools Methods (`src/tools/vault-tools.ts`)

#### `stat(path: string)` Method

**Purpose:** Get comprehensive metadata for any path (file or folder)

**Implementation:**
- Validates path using `PathUtils.isValidVaultPath()`
- Normalizes path using `PathUtils.normalizePath()`
- Checks if path is a file using `PathUtils.resolveFile()`
- If file, returns full `FileMetadata`
- Checks if path is a folder using `PathUtils.resolveFolder()`
- If folder, returns full `DirectoryMetadata`
- If neither, returns `exists: false`

**Returns:** Structured `StatResult` with full metadata when path exists

#### `exists(path: string)` Method

**Purpose:** Fast existence check without fetching full metadata

**Implementation:**
- Validates path using `PathUtils.isValidVaultPath()`
- Normalizes path using `PathUtils.normalizePath()`
- Checks if path is a file using `PathUtils.fileExists()`
- If file, returns `exists: true, kind: "file"`
- Checks if path is a folder using `PathUtils.folderExists()`
- If folder, returns `exists: true, kind: "directory"`
- If neither, returns `exists: false`

**Returns:** Lightweight `ExistsResult` with minimal data

### 3. Tool Registry (`src/tools/index.ts`)

Added two new tool definitions:

#### `stat` Tool

```typescript
{
  name: "stat",
  description: "Get detailed metadata for a file or folder at a specific path...",
  inputSchema: {
    type: "object",
    properties: {
      path: {
        type: "string",
        description: "Vault-relative path to check..."
      }
    },
    required: ["path"]
  }
}
```

#### `exists` Tool

```typescript
{
  name: "exists",
  description: "Quickly check if a file or folder exists at a specific path...",
  inputSchema: {
    type: "object",
    properties: {
      path: {
        type: "string",
        description: "Vault-relative path to check..."
      }
    },
    required: ["path"]
  }
}
```

Added call handlers in `callTool()` switch statement:
```typescript
case "stat":
  return await this.vaultTools.stat(args.path);
case "exists":
  return await this.vaultTools.exists(args.path);
```

---

## Key Features

### Path Validation
- Both tools validate paths before checking existence
- Use `PathUtils.isValidVaultPath()` for consistent validation
- Return clear error messages for invalid paths

### Path Normalization
- Both tools normalize paths using `PathUtils.normalizePath()`
- Ensures consistent behavior across platforms
- Handles Windows backslashes, case sensitivity, etc.

### Structured Results
- Both tools return structured JSON (not plain text)
- Consistent with Phase 2 API unification
- Machine-readable for easy parsing

### Performance Optimization
- `exists()` is optimized for speed (no metadata fetching)
- `stat()` provides comprehensive information when needed
- Clear guidance on when to use each tool

---

## Use Cases

### `stat` Tool

**When to use:**
- Need detailed file/folder information
- Want to check file sizes or modification dates
- Need to distinguish between files and directories with metadata
- Preparing detailed reports or analysis

**Example:**
```typescript
// Get full metadata for a file
const result = await stat("projects/report.md");
// Returns: { exists: true, kind: "file", metadata: { size: 1234, modified: ..., ... } }
```

### `exists` Tool

**When to use:**
- Quick pre-flight checks before operations
- Batch validation of multiple paths
- Simple existence verification
- Performance-critical scenarios

**Example:**
```typescript
// Quick check if folder exists before creating a file
const result = await exists("projects");
// Returns: { path: "projects", exists: true, kind: "directory" }
```

---

## Example Responses

### stat - File Exists

```json
{
  "path": "folder/note.md",
  "exists": true,
  "kind": "file",
  "metadata": {
    "kind": "file",
    "name": "note.md",
    "path": "folder/note.md",
    "extension": "md",
    "size": 1234,
    "modified": 1697500800000,
    "created": 1697400000000
  }
}
```

### stat - Folder Exists

```json
{
  "path": "projects",
  "exists": true,
  "kind": "directory",
  "metadata": {
    "kind": "directory",
    "name": "projects",
    "path": "projects",
    "childrenCount": 5,
    "modified": 0
  }
}
```

### stat - Path Doesn't Exist

```json
{
  "path": "missing/file.md",
  "exists": false
}
```

### exists - File Exists

```json
{
  "path": "folder/note.md",
  "exists": true,
  "kind": "file"
}
```

### exists - Folder Exists

```json
{
  "path": "projects",
  "exists": true,
  "kind": "directory"
}
```

### exists - Path Doesn't Exist

```json
{
  "path": "missing/path",
  "exists": false
}
```

---

## Integration with Existing Code

### Leverages Phase 1 Infrastructure
- Uses `PathUtils` for path validation and normalization
- Uses `ErrorMessages` for consistent error handling
- Follows established patterns from existing tools

### Consistent with Phase 2 API
- Returns structured JSON (not plain text)
- Uses typed result interfaces
- Follows naming conventions (`path` parameter)

### Reuses Metadata Helpers
- Uses `createFileMetadata()` for file metadata
- Uses `createDirectoryMetadata()` for folder metadata
- Ensures consistency with `list_notes` responses

---

## Testing Checklist

- [x] Test `stat` on existing files
- [x] Test `stat` on existing folders
- [x] Test `stat` on non-existent paths
- [x] Test `exists` on existing files
- [x] Test `exists` on existing folders
- [x] Test `exists` on non-existent paths
- [x] Test with various path formats (with/without extensions)
- [x] Test path validation (invalid characters, leading slashes)
- [x] Test path normalization (backslashes, case sensitivity)
- [x] Verify performance difference between `stat` and `exists`

---

## Benefits

### For AI Agents
- Can verify paths before operations
- Can distinguish between files and folders
- Can check file sizes before reading
- Can validate batch operations efficiently

### For Users
- Fewer errors from invalid paths
- Better error messages when paths don't exist
- More predictable behavior

### For Developers
- Reusable path checking logic
- Consistent API patterns
- Easy to extend with more metadata

---

## Future Enhancements

Potential improvements for future phases:

1. **Batch Operations**
   - `stat_many(paths: string[])` for checking multiple paths at once
   - Reduce overhead for bulk validation

2. **Glob Pattern Support**
   - `exists("projects/*.md")` to check if any matching files exist
   - Useful for conditional operations

3. **Metadata Filtering**
   - `stat(path, { fields: ["size", "modified"] })` to fetch only specific fields
   - Optimize performance for specific use cases

4. **Recursive Stats**
   - `stat(path, { recursive: true })` to get stats for all children
   - Useful for directory analysis

---

## Documentation Updates

- [x] Updated `ROADMAP.md` to mark Phase 3 as complete
- [x] Updated `CHANGELOG.md` with Phase 3 changes
- [x] Created `IMPLEMENTATION_NOTES_PHASE3.md` (this file)
- [x] Updated priority matrix in roadmap
- [x] Updated completion statistics

---

## Conclusion

Phase 3 successfully adds essential discovery tools that enable robust path validation and exploration. The implementation is clean, consistent with existing patterns, and provides both detailed (`stat`) and lightweight (`exists`) options for different use cases.

**Next Phase:** Phase 4 (Enhanced List Operations) or Phase 8 (Write Operations & Concurrency) depending on priorities.