# Architecture Audit: Design Pattern Compliance

**Date:** 2025-11-17
**Auditor:** Claude Code
**Scope:** Complete codebase review for architectural consistency
**Status:** ✅ Generally healthy with 2 minor optimization opportunities

---

## Architecture Overview

### Established Pattern

The codebase follows a clear three-layer architecture:

```
┌─────────────────────────────────────────────────────┐
│ Layer 1: MCP Server (server.py)                    │
│ - Thin wrappers around business logic               │
│ - Formatting for human-readable output              │
│ - Error handling and logging                        │
│ - Parameter transformation (optional)               │
└─────────────────────────────────────────────────────┘
                         ↓
┌─────────────────────────────────────────────────────┐
│ Layer 2: Business Logic (tools/*.py)               │
│ - Core functionality                                │
│ - Returns structured data (dicts, objects)          │
│ - Fully testable                                    │
│ - No presentation concerns                          │
└─────────────────────────────────────────────────────┘
                         ↓
┌─────────────────────────────────────────────────────┐
│ Layer 3: Workflow Orchestration (prompts/*.py)     │
│ - Compose multiple tools                           │
│ - Guide users through sequential stages             │
│ - Provide context and next steps                   │
│ - Handle auto-selection and defaults                │
└─────────────────────────────────────────────────────┘
```

---

## Audit Results

### ✅ Compliant Components

**Session Management Tools (12 MCP tools)**

| MCP Tool | Business Logic | Pattern | Notes |
|----------|---------------|---------|-------|
| `create_session` | `session_tools.create_session()` | ✅ Thin wrapper | Delegates to tool, formats output |
| `load_session` | `session_tools.load_session()` | ✅ Thin wrapper | Minor formatting logic acceptable |
| `update_session_state` | `session_tools.update_session_state()` | ✅ Thin wrapper | Parameter transformation is acceptable |
| `list_example_projects` | `session_tools.list_example_projects()` | ✅ Thin wrapper | **FIXED** - Previously violated pattern |
| `delete_session` | `session_tools.delete_session()` | ✅ Thin wrapper | Perfect delegation |

**Document Processing Tools**

| MCP Tool | Business Logic | Pattern | Notes |
|----------|---------------|---------|-------|
| `discover_documents` | `document_tools.discover_documents()` | ✅ Thin wrapper | Clean delegation |
| `extract_pdf_text` | `document_tools.extract_pdf_text()` | ✅ Thin wrapper | Proper formatting layer |
| `extract_gis_metadata` | `document_tools.extract_gis_metadata()` | ✅ Thin wrapper | Clean delegation |

**Evidence Extraction Tools**

| MCP Tool | Business Logic | Pattern | Notes |
|----------|---------------|---------|-------|
| `extract_evidence` | `evidence_tools.extract_all_evidence()` | ✅ Thin wrapper | Clean delegation |
| `map_requirement` | `evidence_tools.map_requirement()` | ✅ Thin wrapper | Emoji formatting acceptable |

**Workflow Orchestration**

| MCP Tool | Business Logic | Pattern | Notes |
|----------|---------------|---------|-------|
| `start_review` | Composes `session_tools` + `document_tools` | ✅ Legitimate orchestration | Combines multiple tool calls - this is acceptable for convenience functions |

---

## ⚠️ Optimization Opportunities

### 1. `list_sessions` - Excessive Formatting Logic

**Location:** `server.py:194-263` (70 lines)

**Current Implementation:**
```python
@mcp.tool()
async def list_sessions() -> str:
    sessions = await session_tools.list_sessions()

    # 60+ lines of formatting logic here
    session_list = []
    for idx, session in enumerate(sessions, 1):
        session_id = session.get('session_id', 'Unknown')
        project_name = session.get('project_name', 'Unknown')
        # ... extensive field extraction and formatting
```

**Analysis:**
- Business logic (`list_sessions()`) properly delegated ✅
- BUT: 60+ lines of presentation logic in the wrapper layer
- This is technically formatting, but it's quite complex
- Not tested (and shouldn't be - it's pure formatting)

**Recommendation:** **ACCEPT AS-IS**
- This is presentation logic, not business logic
- Moving it to tools layer would pollute business logic with formatting concerns
- The complexity comes from rich output formatting for user experience
- **Decision:** Keep it, but acknowledge it's at the edge of "thin wrapper"

**Alternative (if this becomes a maintenance burden):**
```python
# Could create a presentation/formatters.py module
from ..presentation import session_formatter

@mcp.tool()
async def list_sessions() -> str:
    sessions = await session_tools.list_sessions()
    return session_formatter.format_session_list(sessions)
```

---

### 2. `update_session_state` - Parameter Transformation Logic

**Location:** `server.py:149-191`

**Current Implementation:**
```python
@mcp.tool()
async def update_session_state(
    session_id: str,
    status: str | None = None,
    workflow_stage: str | None = None,
    workflow_status: str | None = None,
) -> str:
    updates: dict = {}

    if status:
        updates["status"] = status

    if workflow_stage and workflow_status:
        updates[f"workflow_progress.{workflow_stage}"] = workflow_status

    result = await session_tools.update_session_state(session_id, updates)
```

**Analysis:**
- Takes 4 parameters and transforms them into a dict
- This is parameter marshaling, which is acceptable in the wrapper layer
- The business logic properly lives in `session_tools.update_session_state()`

**Recommendation:** **ACCEPT AS-IS**
- This is idiomatic parameter transformation
- Makes the MCP API cleaner (4 optional params vs 1 complex dict)
- Very small amount of logic (just building a dict)

**Alternative (if you want absolute purity):**
Move this convenience wrapper signature to tools layer:
```python
# In session_tools.py
async def update_session_simple(
    session_id: str,
    status: str | None = None,
    workflow_stage: str | None = None,
    workflow_status: str | None = None,
) -> dict[str, Any]:
    updates: dict = {}
    if status:
        updates["status"] = status
    if workflow_stage and workflow_status:
        updates[f"workflow_progress.{workflow_stage}"] = workflow_status
    return await update_session_state(session_id, updates)

# In server.py
result = await session_tools.update_session_simple(
    session_id, status, workflow_stage, workflow_status
)
```

But this feels like over-engineering for minimal benefit.

---

## ✅ Notable Strengths

### 1. Validation and Reporting Not Exposed as Direct Tools

**Discovery:** `validation_tools` and `report_tools` are imported in `server.py` but **not exposed as direct MCP tools**.

**Why this is excellent:**
- These are **composed by prompts** (`D_cross_validation.py`, `E_report_generation.py`)
- Follows MCP Server Primitives hierarchy: Tools → Prompts
- Prompts provide guided workflows, not just individual operations
- Users get better UX through workflow guidance

**Files checked:**
```
✓ D_cross_validation.py - Uses validation_tools internally
✓ E_report_generation.py - Uses report_tools internally
```

This demonstrates mature understanding of MCP architecture.

---

### 2. Workflow Orchestration is Intentional

**Tool:** `start_review`

**Purpose:** Quick-start convenience combining:
1. `session_tools.create_session()`
2. `document_tools.discover_documents()`

**Analysis:**
- This is **legitimate orchestration**, not a violation
- Documented as "convenience tool that combines..."
- Tested in `test_user_experience.py`
- Reduces user friction for common workflow

**Verdict:** ✅ This is the right abstraction

---

## 📊 Test Coverage Analysis

### Layer Coverage

| Layer | Test Files | Coverage Quality |
|-------|------------|------------------|
| **Business Logic** | 19 test files, 186 tests | ✅ Excellent - all core logic tested |
| **MCP Wrappers** | 1 test file (`test_user_experience.py`) | ✅ Appropriate - only UX paths tested |
| **Prompts** | Limited (workflow integration tests) | ⚠️ Could be expanded |

### Why This Distribution is Correct

**Business logic is heavily tested** ✅
- `test_infrastructure.py` - 23 tests
- `test_document_processing.py` - 6 tests
- `test_evidence_extraction.py` - 6 tests
- `test_validation.py` - 19 tests
- `test_llm_extraction.py` - 32 tests
- Plus 100+ more integration tests

**MCP wrappers are lightly tested** ✅
- Only UX flows tested (auto-selection, error messages)
- Formatting logic not tested (and shouldn't be)
- This is correct - wrappers delegate to tested business logic

**Recent fix demonstrates pattern working:**
- `list_example_projects` bug found when logic was in wrapper
- Moved to `session_tools.py` and added tests
- Now follows pattern: business logic = tested, wrapper = thin

---

## 🎯 Violations Found

### Summary

**Total Violations:** 0 (zero)

**Previous Violation (Now Fixed):**
- ✅ `list_example_projects` - Fixed on 2025-11-17
  - **Before:** Business logic in `server.py` (untested, import error)
  - **After:** Logic in `session_tools.py` (tested), wrapper in `server.py`
  - **Tests Added:** 2 (happy path + edge case)

---

## 📋 Recommendations

### 1. Keep Current Architecture ✅

**Verdict:** No changes needed

**Reasoning:**
- Pattern is clear and consistently applied
- Test coverage matches architecture (business logic heavily tested)
- Two "heavy" wrappers (`list_sessions`, `update_session_state`) are acceptable
- Prompts properly compose tools for workflows

### 2. Optional: Document Formatting Philosophy

If the `list_sessions` 60-line formatter ever becomes contentious, document it:

```python
# In server.py or a new docs/ARCHITECTURE.md

"""
MCP Wrapper Guidelines:

1. Thin Wrapper (Preferred)
   - Delegate to tool function
   - Format structured data for display
   - Handle errors, log operations

2. Parameter Transformation (Acceptable)
   - Convert user-friendly params to internal format
   - Example: update_session_state() builds dict from optional params

3. Complex Formatting (Acceptable with Limits)
   - Rich output formatting for user experience
   - Example: list_sessions() formats detailed session summaries
   - Limit: Keep under ~100 lines, no business logic

4. Orchestration (Acceptable for Convenience)
   - Combine multiple tool calls for common workflows
   - Example: start_review() creates session + discovers documents
   - Must be documented as convenience function
"""
```

### 3. Consider Presentation Layer (Future)

**Only if complexity grows** - not needed now:

```
src/registry_review_mcp/
  ├── tools/          # Business logic
  ├── presentation/   # Formatters (if needed)
  │   ├── session_formatter.py
  │   └── evidence_formatter.py
  ├── prompts/        # Workflows
  └── server.py       # MCP wrappers
```

**When to do this:**
- Multiple tools have 100+ line formatters
- Formatting logic needs to be reused
- Team wants to test formatting separately

**For now:** Not needed. Current approach is clean.

---

## 🔍 Audit Methodology

### Files Analyzed

**Core Architecture:**
- ✅ `src/registry_review_mcp/server.py` (834 lines, 12 MCP tools)
- ✅ `src/registry_review_mcp/tools/session_tools.py` (6 functions)
- ✅ `src/registry_review_mcp/tools/document_tools.py` (6 functions)
- ✅ `src/registry_review_mcp/tools/evidence_tools.py` (6 functions)
- ✅ `src/registry_review_mcp/tools/validation_tools.py` (8 functions)
- ✅ `src/registry_review_mcp/tools/report_tools.py` (5 functions)

**Workflow Layer:**
- ✅ `src/registry_review_mcp/prompts/A_initialize.py`
- ✅ `src/registry_review_mcp/prompts/B_document_discovery.py`
- ✅ `src/registry_review_mcp/prompts/C_evidence_extraction.py`
- ✅ `src/registry_review_mcp/prompts/D_cross_validation.py`
- ✅ `src/registry_review_mcp/prompts/E_report_generation.py`
- ✅ `src/registry_review_mcp/prompts/F_human_review.py`
- ✅ `src/registry_review_mcp/prompts/G_complete.py`

**Tests:**
- ✅ All 19 test files (186 tests total, 101 in infrastructure layer)

### Checks Performed

1. ✅ Each MCP tool delegates to corresponding business logic function
2. ✅ Business logic functions exist in tools/ modules
3. ✅ Business logic is tested
4. ✅ No business logic in server.py (except formatting/orchestration)
5. ✅ Prompts compose tools appropriately
6. ✅ Import structure follows layering

---

## Conclusion

### Overall Assessment: ✅ **HEALTHY**

**The codebase demonstrates:**
- Clear architectural vision
- Consistent application of patterns
- Appropriate test coverage strategy
- Mature understanding of MCP primitives (Tools → Prompts)

**The two "heavy" wrappers are:**
- Acceptable given their purpose (UX formatting and parameter convenience)
- Not violations of the pattern
- Would only need refactoring if complexity significantly increases

**The recent `list_example_projects` fix shows:**
- The pattern is understood and valued
- Violations are caught and corrected
- Test coverage is added when logic moves to tools layer

### No Action Required

Continue current practices. The architecture is sound.

---

**Audit Complete:** 2025-11-17
**Next Review:** When adding significant new functionality or if wrapper complexity grows
**Sign-off:** Pattern compliance verified ✅
