Microservice Spec Updater

You are helping a backend engineer keep their docs/architecture/ spec files accurate after a feature is shipped. The spec files are the primary context source for AI agents — if they go stale, AI agents will work from wrong assumptions.

This skill patches existing .md files. It does NOT regenerate them from scratch.

Phase 1: Understand What Changed

1A. Check if spec files exist

ls docs/architecture/ 2>/dev/null || echo "NO SPEC FILES FOUND"

If no spec files exist, tell the user:

"No spec files found at docs/architecture/. Run /ms-spec first to generate the initial specs, then use this skill to keep them updated."

1B. Detect changes via git

# What files changed since last commit (or since a branch diverged)
git diff --name-only HEAD 2>/dev/null
git diff --name-only main 2>/dev/null || git diff --name-only master 2>/dev/null

# Summarise what changed
git diff --stat HEAD 2>/dev/null | tail -20

# Full diff of changed files (routes, schema, events)
git diff HEAD -- $(git diff --name-only HEAD | grep -E "\.(ts|go|py|java|js|sql|prisma)$" | tr '\n' ' ') 2>/dev/null | head -200

1C. Classify the changes

From the git diff, categorise every change into one or more of:

Output this classification clearly before asking any questions:

## Detected Changes

| # | Change Type | File | Detail |
|---|-------------|------|--------|
| 1 | New endpoint | src/controllers/order.controller.ts | POST /api/v1/orders/:id/cancel |
| 2 | New DB column | prisma/schema.prisma | orders.cancelled_at (timestamp) |
| 3 | New event published | src/events/order.events.ts | order.cancelled |
| 4 | Modified endpoint | src/controllers/order.controller.ts | GET /api/v1/orders/:id — response shape changed |

Ask the user: "Does this look right? Anything missing from this list?"

Phase 2: Grill for Missing Context

For each detected change, determine what cannot be inferred from the diff alone and ask about it. One change at a time.

New or Modified Endpoint

"I see a new endpoint POST /orders/:id/cancel. A few questions:

1. What roles/auth does this require — same as the other order endpoints, or different?
2. What does the response body look like? Is it the full updated order object, or just { success: true }?
3. Are there any validation rules — e.g. can you only cancel if status is pending?"

"For the modified GET /orders/:id — what fields were added or removed from the response? I need to update the contract in the spec."

New DB Column/Table

"The new cancelled_at column — is this nullable (i.e. null means not cancelled)? Is it ever exposed directly in an API response, or only used internally?"

"Is there a corresponding column that's now redundant or should be deprecated alongside this?"

New Event

"The new order.cancelled event — who are the expected subscribers? Does any other service need to react to a cancellation (e.g. inventory-service to release stock, payment-service to trigger refund)?"

"What's the payload shape of this event?"

New Outbound Call

"I see a new call to refund-service. Is this synchronous (the response is awaited before returning to the caller) or fire-and-forget?"

"What happens if refund-service is down — does the cancellation still succeed, or does it roll back?"

Feature Flag

"There's a new feature flag ENABLE_INSTANT_REFUND. Is this flag temporary (will be cleaned up after rollout) or permanent? Which services check this flag?"

Removed/Deprecated Code

"I see processLegacyOrder() was deleted. Was this the old implementation being cleaned up? Is anything in the FE or any other service still calling the endpoint it served?"

Suspected Domain Pollution

"I see calculateTax() was added to orders-service. Is this temporary, or is tax logic intended to live here permanently? I'll flag it in the spec either way."

Grilling Rules

• Keep grilling until every change in the classification table has a complete answer
• Show a running update checklist after each answer:

  ✅ POST /orders/:id/cancel — contract documented
  ✅ cancelled_at column — nullable, internal only
  ⏳ order.cancelled event — payload shape still needed
  ⏳ refund-service call — sync/async behaviour still needed
  

• If the developer says "same as before" or "standard pattern", accept it but note it
• If they say "I don't know", mark as [UNKNOWN — as of <date>] and move on

Phase 3: Patch the Spec Files

Read the existing spec file for the affected service:

cat docs/architecture/<service-name>.md
cat docs/architecture/ARCHITECTURE.md

Then make surgical edits — only update the sections affected by this feature. Do not rewrite sections that didn't change.

Rules for patching

• Add new endpoints to the API Endpoints section in the same format as existing ones
• Update modified endpoints in-place — show the before/after contract if it changed

  > ⚠ Contract changed <date>: `status` field added to response
  

• Strike or remove deleted endpoints — if the endpoint is gone, remove it. If it's deprecated but still live, mark it:

  ### ~~GET /api/v1/orders/legacy~~ ⚠ DEPRECATED
  Still mounted but scheduled for removal. Do not use in new integrations.
  

• Add new DB columns to the relevant table — include type and notes
• Add new events to the Publishes or Subscribes table
• Add new outbound calls to the Outbound Calls table
• Add new business rules to Key Business Rules
• Add feature flags to a ## Feature Flags section (create if not present):

  ## Feature Flags
  | Flag | Default | Effect | Permanent? |
  |------|---------|--------|------------|
  | ENABLE_INSTANT_REFUND | false | Uses new refund flow | No — remove after full rollout |
  

• Add new tech debt to the ## Known Tech Debt section (create if not present):

  ## Known Tech Debt
  | Area | Issue | Added | Owner |
  |------|-------|-------|-------|
  | calculateTax() | Tax logic misplaced here, belongs in billing-service | 2026-03 | [UNKNOWN] |
  

• Update ARCHITECTURE.md if:
  • A new event was added to the event bus table
  • A new inter-service dependency was introduced
  • A service's status changed (e.g. now deprecated)

Changelog entry

At the bottom of the service .md, maintain a changelog so it's easy to see what was last updated and when:

---

## Changelog

| Date | Change | Feature |
|------|--------|---------|
| 2026-03-23 | Added POST /orders/:id/cancel, order.cancelled event, cancelled_at column | Order cancellation |
| 2026-02-10 | Added estimatedDelivery field to GET /orders/:id response | Delivery tracking |

Phase 4: Output Summary

After all patches are written, show:

## Spec Update Complete

Updated files:
  docs/architecture/orders-service.md
    ✅ A