---
name: ln-113-backend-docs-creator
description: "Creates backend docs (api_spec.md, database_schema.md). Use when project has backend API or database."
license: MIT
model: claude-sonnet-4-6
---

> **Paths:** File paths (`references/`, `../ln-*`) are relative to this skill directory.

# Backend Documentation Creator

**Type:** L3 Worker

L3 Worker that creates 2 backend documentation files. CONDITIONAL - only invoked when project has backend or database.

## Purpose & Scope
- Creates api_spec.md (if hasBackend)
- Creates database_schema.md (if hasDatabase)
- Receives Context Store from ln-110-project-docs-coordinator
- OpenAPI 3.0 compliant API specification
- ER diagrams in Mermaid for database schema
- Never gathers context itself; uses coordinator input

## Invocation (who/when)
- **ln-110-project-docs-coordinator:** CONDITIONALLY invoked when:
  - `hasBackend=true` (express, fastify, nestjs, fastapi detected)
  - `hasDatabase=true` (pg, mongoose, prisma, sequelize detected)
- Never called directly by users

## Inputs
From coordinator:
- `contextStore`: Context Store with backend-specific data
  - API_TYPE (REST, GraphQL, gRPC)
  - API_ENDPOINTS (from route scan)
  - AUTH_SCHEME (JWT, OAuth2, API keys)
  - DATABASE_TYPE (PostgreSQL, MongoDB, MySQL)
  - SCHEMA_OVERVIEW (from migrations/models)
  - ER_DIAGRAM (generated from schema)
- `targetDir`: Project root directory
- `flags`: { hasBackend, hasDatabase }

**MANDATORY READ:** Load `references/docs_quality_contract.md`, and `references/markdown_read_protocol.md`.
Optional rule catalog: load `references/docs_quality_rules.json` only when exact rule IDs, path matrices, or allowlisted placeholder exceptions are needed.

## Documents Created (2, conditional)

| File | Condition | Questions | Auto-Discovery |
|------|-----------|-----------|----------------|
| docs/project/api_spec.md | hasBackend | Q39-Q40 | Medium |
| docs/project/database_schema.md | hasDatabase | Q41-Q42 | High |

## Workflow

### Phase 1: Check Conditions
1. Parse flags from coordinator
2. If `!hasBackend && !hasDatabase`: return early with empty result
3. Determine which documents to create

### Phase 2: Create Documents
For each applicable document:
1. Check if file exists (idempotent)
2. If exists: skip with log
3. If not exists:
   - Copy template
   - Replace placeholders with Context Store values
   - Preserve the shared opening contract and standard top sections from the template
   - Generate ER diagram for database_schema.md
   - Never leave template markers in published backend docs
   - If data is missing: omit the claim or use a concise neutral fallback, but do NOT emit `[TBD: ...]`

### Phase 3: Self-Validate
1. Check SCOPE tag and metadata markers
2. Check required top sections (`Quick Navigation`, `Agent Entry`, `Maintenance`)
3. Validate format:
   - api_spec.md: endpoint table, request/response examples
   - database_schema.md: ER diagram, table definitions
4. Check docs-quality contract compliance (no forbidden placeholders, no leaked template metadata, valid doc kind/role)

### Phase 4: Return Status
```json
{
  "created_files": ["docs/project/api_spec.md"],
  "skipped_files": ["docs/project/database_schema.md"],
  "quality_inputs": {
    "doc_paths": ["docs/project/api_spec.md", "docs/project/database_schema.md"],
    "owners": {
      "docs/project/api_spec.md": "ln-113-backend-docs-creator",
      "docs/project/database_schema.md": "ln-113-backend-docs-creator"
    }
  },
  "validation_status": "passed"
}
```

## Critical Notes
- **Conditional:** Skip entirely if no backend/database detected
- **OpenAPI compliant:** api_spec.md follows OpenAPI 3.0 structure
- **ER diagrams:** Generated in Mermaid erDiagram format
- **Idempotent:** Never overwrite existing files
- **Publishable output:** No `[TBD: ...]`, `TODO`, or leaked template metadata in backend docs

### NO_CODE_EXAMPLES Rule (MANDATORY)
API spec documents **contracts**, NOT implementations:
- **ALLOWED in api_spec.md:** JSON request/response schemas (this IS the API contract), endpoint tables
- **FORBIDDEN:** Controller implementations, validation classes, service code, middleware examples
- **TEMPLATE RULE:** api_spec_template.md includes `<!-- NO_CODE_EXAMPLES: ... -->` tag - FOLLOW IT

### Stack Adaptation Rule (MANDATORY)
- Links must reference stack-appropriate docs (Microsoft for .NET, MDN for JS)
- API examples must match project stack (Express for Node.js, FastAPI for Python)

### Format Priority (MANDATORY)
Tables (endpoints, schemas) > Mermaid (ER diagrams) > Lists > Text

## Runtime Summary Artifact

**MANDATORY READ:** Load `references/docs_generation_summary_contract.md`

Accept optional `summaryArtifactPath`.

Summary kind:
- `docs-generation`

Required payload semantics:
- `worker = "ln-113"`
- `status`
- `created_files`
- `skipped_files`
- `quality_inputs`
- `validation_status`
- `warnings`

Write the summary to the provided artifact path or return the same envelope in structured output.

## Definition of Done
- [ ] Conditions checked (hasBackend, hasDatabase)
- [ ] Applicable documents created
- [ ] ER diagram generated (if database_schema.md created)
- [ ] Self-validation passed (metadata markers, top sections, format)
- [ ] **Actuality verified:** all document facts match current code (paths, functions, APIs, configs exist and are accurate)
- [ ] Status returned

## Reference Files
- Templates: `references/templates/api_spec_template.md`, `references/templates/database_schema_template.md`
- Questions: `references/questions_backend.md` (Q39-Q42)

---
**Version:** 1.2.0
**Last Updated:** 2025-01-12