Technical Spec Bridge

Technical Spec Bridge

Overview

The gap between "what users need" and "what engineers build" is where miscommunication happens. A technical spec bridge translates product requirements into engineering-ready specifications: API contracts, data models, state machines, error handling, and non-functional requirements. This skill helps PMs work effectively with engineering by providing the right level of technical detail.

When to Use

• Handing off PRDs to engineering for implementation
• Writing API specifications for new features
• Defining data models and schema changes
• Scoping technical work for estimation
• Don't use for: overriding engineering design decisions (specs are guidance), front-end only changes (design specs may be sufficient)

Instructions

1. Map Product Requirements to Technical Components

For each requirement in the PRD, identify:

• Data model: What new entities or fields are needed?
• API endpoints: What needs to be created or modified?
• Business logic: What rules need to be implemented?
• UI components: What new screens or components?
• Integrations: What external services need to be connected?

2. Define API Contracts

For each API endpoint that needs to change:

## [Method] /api/[resource]
- **Purpose**: What this endpoint does
- **Auth**: What authentication is required
- **Request**: 
  - Query params: [name, type, required, description]
  - Body: [field, type, required, description]
- **Response (200)**:
  - [field, type, description]
- **Error responses**:
  - 400: [when it occurs]
  - 401: [when it occurs]
  - 403: [when it occurs]
  - 404: [when it occurs]
  - 500: [when it occurs]
- **Rate limiting**: [limits if applicable]

3. Document Data Models

Define entities and their relationships:

## [Entity Name]
- **id**: UUID, primary key
- **name**: string, required, max 100 chars
- **status**: enum(pending, active, archived), default: pending
- **created_by**: FK → users.id, required
- **Relationships**:
  - belongs_to :team
  - has_many :updates
  - has_many :members through: :team_memberships

4. Specify State Machines

For entities with multiple states:

## Order States
          ┌─────────┐
          │ Pending │
          └────┬────┘
         ┌─────┴──────┐
         ▼            ▼
    ┌────────┐  ┌─────────┐
    │ Active │  │ Canceled│
    └───┬────┘  └─────────┘
        ▼
   ┌─────────┐
   │ Archived│
   └─────────┘

Transitions:
- Pending → Active: payment_confirmed
- Pending → Canceled: user_cancelled
- Active → Archived: after_90_days
- Active → Canceled: admin_cancelled

5. Define Error States and Edge Cases

For each operation, specify:

• Success path: The normal flow
• Validation errors: What happens with invalid input
• Business rule violations: What happens when rules are broken
• System errors: Timeouts, rate limits, service unavailable
• Race conditions: What happens with concurrent operations

6. Document Non-Functional Requirements

• Performance: P95 latency targets, throughput expectations
• Scalability: Expected load, growth projections
• Availability: Uptime requirements, SLAs
• Security: Authentication, authorization, data privacy
• Compliance: Regulatory requirements (GDPR, SOC2, etc.)

Sample Output

Requirement from PRD: "Users can post status updates that appear on their team's timeline"

API Contract:

POST /api/v1/updates
Purpose: Create a new status update
Auth: Bearer token, user must be a team member
Request body:
  team_id: UUID, required
  content: string, required, max 5000 chars
  status: enum(on_track, needs_help, blocked), required
  attachments: array of URLs, optional, max 5

Response (201):
  id: UUID
  content: string
  status: string
  author: { id, name, avatar_url }
  created_at: ISO8601

Error responses:
  400: Invalid content (empty or too long)
  401: Authentication required
  403: User is not a member of this team
  404: Team not found
  422: Validation failed (missing required field)
  429: Rate limit exceeded (10 requests/minute)

Common Pitfalls

1. Over-specifying implementation — Tell engineering WHAT needs to happen, not HOW to code it
2. Ignoring error states — The happy path is easy. Error handling is 50% of the work
3. Changing requirements mid-implementation — Spec changes cost 10x more during implementation
4. Not involving engineering in the spec — A spec written in isolation will miss technical constraints
5. Forgetting edge cases — "What if there's no data?" is as important as "what if it works?"

Verification Checklist

• [ ] API contracts defined with request/response shapes and error codes
• [ ] Data models documented with fields, types, and relationships
• [ ] State machines defined for entities with multiple states
• [ ] Error states and edge cases documented
• [ ] Non-functional requirements captured (performance, scalability, security)
• [ ] Engineering reviewed and signed off on the spec

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: uthumany
• Source: uthumany/uthy-legacy-os
• License: MIT
• Homepage: https://uthumany.github.io/uthy-legacy-os/

Install and usage instructions live in the source repository linked above.