Implementation Fidelity Review Skill

Table of Contents

• Overview
• Skill Family
• When to Use
• MCP Tooling
• Core Workflow
• LSP Operations Quick Reference
• Essential Commands
• Review Types
• Assessment Categories
• Long-Running Operations
• Example Invocation

Overview

The sdd-review skill compares actual implementation against SDD specification requirements. It uses LSP for structural verification and MCP for AI-powered deviation analysis.

Skill Family

Part of the Spec-Driven Development quality assurance family:

sdd-plan → sdd-implement → [CODE] → sdd-review (this skill) → run-tests → sdd-pr

When to Use This Skill

Use when:

• Verifying implementation matches specification requirements
• Identifying deviations between plan and actual code
• Reviewing pull requests for spec compliance
• Auditing completed phases or tasks

Do NOT use for:

• Creating specifications (use sdd-plan)
• Finding next tasks or tracking progress (use sdd-implement)
• Running tests (use run-tests)

Flow

[x?]=decision · (GATE)=user approval · →=sequence · ↻=loop · §=section ref

- **Entry** → [Familiar with code?]
  - [no] → Explore subagent (optional)
  - [yes] → skip
- SpecChanges → `spec action="diff"` + `spec action="history"`
  - Identify changed requirements, new tasks
- LSP PreCheck → `documentSymbol` → [structures exist?]
  - [fail] → early exit with findings
  - [pass] → continue
- MCP Review → `fidelity action="review"` [phase|task] (up to 5 min)
  - [deviations found?] ↻ LSP Investigate
    - `goToDefinition` → `findReferences` → `incomingCalls`
  - Assess[Exact|Minor|Major|Missing]
- **Exit** → Report with recommendations

MCP Tooling

This skill uses the Foundry MCP server with router+action pattern: mcp__plugin_foundry_foundry-mcp__<router> with action="<action>".

Critical Rules:

• ALWAYS use MCP tools for spec operations
• NEVER use Read() on spec JSON files
• NEVER use shell commands (cat, grep, jq) on specs

Router Actions

Router	Action	Purpose
review	fidelity	Run AI-powered fidelity analysis
task	query	List tasks for review scope
task	info	Get task details and acceptance criteria
spec	diff	Compare spec versions to understand changes
spec	history	View spec modification timeline

Spec Comparison for Fidelity Context

Use spec:diff and spec:history to understand what changed before reviewing implementation:

# See what changed since last review
mcp__plugin_foundry_foundry-mcp__spec action="diff" spec_id="{spec-id}" compare_to="specs/.backups/{spec-id}-previous.json"

# View modification history to understand evolution
mcp__plugin_foundry_foundry-mcp__spec action="history" spec_id="{spec-id}" limit=5

Why this helps fidelity review:

• diff: Identifies which requirements changed, helping focus review on modified tasks
• history: Shows when requirements were added/modified, explaining apparent deviations that were actually spec updates

Core Workflow

The fidelity review workflow integrates LSP verification with MCP AI analysis:

Step 1: Gather Context (Optional)

For unfamiliar code, use Explore subagent to find implementation files:

Explore agent (medium thoroughness): Find all files in phase-1, related tests, config files

Step 2: Check Spec Changes

Before reviewing, understand what changed in the spec since the last review:

# Check recent spec modifications
mcp__plugin_foundry_foundry-mcp__spec action="history" spec_id="{spec-id}" limit=5

# Compare current spec against last backup
mcp__plugin_foundry_foundry-mcp__spec action="diff" spec_id="{spec-id}" compare_to="specs/.backups/{spec-id}-last-review.json"

Deviation assessment using diff:

📊 Spec Diff: user-auth-001

Tasks:
  ~ task-1-2: Acceptance criteria updated (added "support OAuth2")
  + task-1-4: New task added after initial implementation

Use this to:
- Focus review on changed requirements (task-1-2)
- Flag new tasks as "not yet implemented" rather than "deviation" (task-1-4)
- Explain apparent deviations that reflect spec evolution

Step 3: LSP Structural Pre-Check

Before the AI review, verify structural requirements with LSP:

# Get symbols in implementation file
symbols = LSP(operation="documentSymbol", filePath="src/auth/service.py", line=1, character=1)

# Compare against spec: expects AuthService with login(), logout(), refresh_token()
# Identify missing symbols before expensive AI review

Why: Catches missing implementations in seconds before 5-minute AI review.

Step 4: MCP Fidelity Review

Run the AI-powered fidelity analysis:

# Phase review
mcp__plugin_foundry_foundry-mcp__review action="fidelity" spec_id="{spec-id}" phase_id="{phase-id}"

# Task review
mcp__plugin_foundry_foundry-mcp__review action="fidelity" spec_id="{spec-id}" task_id="{task-id}"

The MCP tool handles spec loading, implementation analysis, AI consultation, and report generation.

Step 5: LSP-Assisted Investigation

For deviations found, use LSP to investigate:

# Trace deviation origin
definition = LSP(operation="goToDefinition", filePath="src/auth/service.py", line=45, character=10)

# Find what depends on deviated code
calls = LSP(operation="incomingCalls", filePath="src/auth/service.py", line=45, character=10)

# Assess blast radius
refs = LSP(operation="findReferences", filePath="src/auth/service.py", line=45, character=10)

Why: Understand deviation impact before recommending fixes.

For detailed LSP patterns and examples, see references/lsp-integration.md

LSP Operations Quick Reference

Operation	When to Use	Purpose
documentSymbol	Pre-check	List all symbols in a file for structural verification
workspaceSymbol	Pre-check	Find symbols across codebase
hover	During review	Get type info and documentation
goToDefinition	Investigation	Trace where symbols are defined
findReferences	Investigation	Find all usages of a symbol
incomingCalls	Investigation	Find what calls a function
outgoingCalls	Investigation	Find what a function calls

Essential Commands

Query tasks before review:

mcp__plugin_foundry_foundry-mcp__task action="query" spec_id="{spec-id}" parent="{phase-id}"

Phase review:

mcp__plugin_foundry_foundry-mcp__review action="fidelity" spec_id="{spec-id}" phase_id="{phase-id}"

Task review:

mcp__plugin_foundry_foundry-mcp__review action="fidelity" spec_id="{spec-id}" task_id="{task-id}"

For query patterns and anti-patterns, see references/querying.md

Review Types

Type	Scope	When to Use
Phase Review	3-10 tasks	Phase completion checkpoints
Task Review	1 file	Critical task validation, high-risk implementations

For detailed workflow per review type, see references/review-types.md

Fidelity Assessment Categories

Category	Meaning
Exact Match	Implementation precisely matches specification
Minor Deviation	Small differences with no functional impact
Major Deviation	Significant differences affecting functionality
Missing	Specified features not implemented

Long-Running Operations

This skill may take up to 5 minutes. The MCP tool handles timeout internally.

Never use run_in_background=True with frequent polling.

Example Invocation

Skill(foundry:sdd-review) "Review phase phase-1 in spec user-auth-001"

Detailed Reference

For comprehensive documentation including:

• Long-running operations guidance → references/long-running.md
• Review types → references/review-types.md
• LSP integration patterns → references/lsp-integration.md
• Querying spec data → references/querying.md
• Workflow steps → references/workflow.md
• Report structure → references/report.md
• SDD workflow integration → references/integration.md
• Assessment categories → references/assessment.md
• Examples → references/examples.md
• Error handling → references/errors.md
• Best practices → references/best-practices.md
• Subagent patterns → references/subagent.md