Using Serena For Exploration

Using Serena for Exploration

Use this skill when exploring codebases with Serena MCP tools for architectural understanding and pattern discovery.

Core Principles

• Start broad, narrow progressively
• Use symbolic tools before reading full files
• Always provide file:line references
• Minimize token usage through targeted reads

Workflow

1. Initial Discovery

Use list_dir and find_file to understand project structure:

# Get repository overview
list_dir(relative_path=".", recursive=false)

# Find specific file types
find_file(file_mask="*auth*.py", relative_path="src")

2. Symbol Overview

Use get_symbols_overview before reading full files:

# Get top-level symbols in a file
get_symbols_overview(relative_path="src/auth/handler.py")

Returns classes, functions, imports - understand structure without reading bodies.

3. Targeted Symbol Reading

Use find_symbol for specific code:

# Read a specific class without body
find_symbol(
    name_path_pattern="AuthHandler",
    relative_path="src/auth/handler.py",
    include_body=false,
    depth=1  # Include methods list
)

# Read specific method with body
find_symbol(
    name_path_pattern="AuthHandler/login",
    relative_path="src/auth/handler.py",
    include_body=true
)

Name path patterns:

• Simple name: "login" - matches any symbol named "login"
• Relative path: "AuthHandler/login" - matches method in class
• Absolute path: "/AuthHandler/login" - exact match within file
• With index: "AuthHandler/login[0]" - specific overload

4. Pattern Searching

Use search_for_pattern when you don't know symbol names:

# Find all JWT usage
search_for_pattern(
    substring_pattern="jwt\\.encode",
    relative_path="src",
    restrict_search_to_code_files=true,
    context_lines_before=2,
    context_lines_after=2,
    output_mode="content"
)

Pattern matching:

• Uses regex with DOTALL flag (. matches newlines)
• Non-greedy quantifiers preferred: .*? not .*
• Escape special chars: \\{\\} for literal braces

5. Relationship Discovery

Use find_referencing_symbols to understand dependencies:

# Who calls this function?
find_referencing_symbols(
    name_path="authenticate_user",
    relative_path="src/auth/handler.py"
)

Returns code snippets around references with symbolic info.

Reporting Format

Always structure findings as:

## Codebase Findings

### Current Architecture
- **Authentication:** `src/auth/handler.py:45-120`
  - JWT-based auth with refresh tokens
  - Session storage in Redis

### Similar Implementations
- **User management:** `src/users/controller.py:200-250`
  - Uses similar validation pattern
  - Can reuse `validate_credentials()` helper

### Integration Points
- **Middleware:** `src/middleware/auth.py:30`
  - Hook new auth method here
  - Follows pattern: check → validate → attach user

Anti-Patterns

❌ Don't: Read entire files before understanding structure ✅ Do: Use get_symbols_overview first

❌ Don't: Use full file reads for symbol searches ✅ Do: Use find_symbol with targeted name paths

❌ Don't: Search without context limits ✅ Do: Use relative_path to restrict search scope

❌ Don't: Return findings without file:line references ✅ Do: Always include exact locations: file.py:123-145

Token Efficiency

• Overview tools use ~500 tokens vs. ~5000 for full file
• Targeted symbol reads use ~200 tokens per symbol
• Pattern search with head_limit=20 caps results
• Use depth=0 if you don't need child symbols

Example Session

# 1. Find auth-related files
files = find_file(file_mask="*auth*.py", relative_path="src")
# → Found: src/auth/handler.py, src/auth/middleware.py

# 2. Get overview of main handler
overview = get_symbols_overview(relative_path="src/auth/handler.py")
# → Classes: AuthHandler
# → Functions: authenticate_user, validate_token

# 3. Read specific method
method = find_symbol(
    name_path_pattern="AuthHandler/authenticate_user",
    relative_path="src/auth/handler.py",
    include_body=true
)
# → Got full implementation of authenticate_user

# 4. Find who calls this
refs = find_referencing_symbols(
    name_path="authenticate_user",
    relative_path="src/auth/handler.py"
)
# → Called from: middleware.py:67, api/routes.py:123