FSD Generator
Translates PRDs into actionable, technical functional specification documents.
Install
mkdir -p .claude/skills/fsd-generator && curl -L -o skill.zip "https://agentskills.codes/api/skills/download/15505" && unzip -o skill.zip -d .claude/skills/fsd-generator && rm skill.zipInstalls to .claude/skills/fsd-generator
Activation
This is the description your AI agent reads to decide when to run this skill — the better it matches your request, the more reliably it fires.
Generate comprehensive Functional Specification Documents (FSDs) that translate PRD requirements into implementation-ready specifications. Use when the user needs to create an FSD, functional spec, system specification, or detailed feature specification. Triggers on requests like "create an FSD", "write functional specifications", "translate this PRD into specs", or any request to define system behaviors, data requirements, business rules, and acceptance criteria from a PRD or feature description.Key capabilities
- →Translate PRD requirements into implementation-ready functional specifications
- →Define system behaviors and data requirements
- →Identify and list acceptance criteria using Given-When-Then format
- →Prioritize features using MoSCoW (Must/Should/Could/Won't)
- →Generate Global FSDs including system architecture and global business rules
- →Produce Feature FSDs detailing functional logic, UI states, and validation rules
How it works
The skill analyzes a PRD or context, extracts key information, and generates an FSD by applying specific writing rules and structuring the document based on whether it's a global or feature FSD.
Inputs & outputs
When to use FSD Generator
- →Creating fsd from prd
- →Writing feature specifications
- →Defining system business rules
About this skill
Functional Specification Document (FSD) Generator
Role
Senior Technical Business Analyst and Solutions Architect. Specializes in translating PRDs into implementation-ready functional specifications that bridge business vision and technical implementation.
Objective
Generate a complete FSD that converts PRD requirements into precise functional specifications, system behaviors, data requirements, and acceptance criteria — usable directly by development teams.
Process
Step 1: Check Mode
Mode A: Global FSD (Default)
Trigger: "Create FSD", "Project Kickoff", or no context.
Goal: Create docs/fsd.md.
Mode B: Feature FSD
Trigger: "Feature FSD", "Feature Spec", or specific feature context.
Goal: Create docs/features/[feature]/fsd.md.
Step 2: Analyze the PRD/Context
Key Analysis Rules:
- Traceability: Every FSD item must map to a PRD requirement.
- MoSCoW: Prioritize features (Must/Should/Could/Won't).
- Gaps: Identify vague requirements and list them as "Open Questions".
Extract:
- Global: System-wide patterns, Roles/Permissions, Integration constraints.
- Feature: Specific user stories, Acceptance Criteria, Edge cases.
Step 3: Generate Output
Writing Style Rules:
- Use precise language: "System SHALL..." (mandatory) vs "System MAY..." (optional).
- Define Atomic Business Rules (
BR-XXX). - Use Given-When-Then for acceptance criteria.
- Include Negative Scenarios (what happens when things go wrong).
If Mode A (Global FSD):
Produce docs/fsd.md focusing on:
- System Architecture: High-level diagrams, tech stack integration strategy.
- Global Business Rules: Permissions, standard workflows, validations.
- Data Dictionary: Core entities, types, and relationships.
- API Standards: Error formats, pagination, auth flows.
If Mode B (Feature FSD):
Produce docs/features/[feature]/fsd.md focusing on:
- Functional Logic: Detailed steps for every user interaction (Happy Path + Alt Paths).
- UI States: Loading, Empty, Partial, Error, Success.
- Validation Rules: Field-level validation (types, lengths, regex).
- Edge Cases: Network failures, race conditions, concurrent editing.
- Mermaid Flows: Sequence diagrams for complex logic.
- Traceability Matrix: Link
FR-XXXtoUS-XXX.
Step 4: Review & Refine
Present the generated FSD for review. Iterate on feedback.
Quality Checklist
- Every PRD requirement maps to at least one functional specification
- All requirements are SMART (Specific, Measurable, Achievable, Relevant, Testable)
- Each acceptance criterion is verifiable by QA
- Business rules are atomic and non-contradictory
- Data specifications cover all functional requirements
- Traceability matrix links every PRD item to FSD requirements
When not to use it
- →When the user needs a Product Requirements Document (PRD)
- →When the task is not related to defining system behaviors or data requirements
- →When the output is not intended for development teams
Limitations
- →Every FSD item must map to a PRD requirement
- →The skill identifies vague requirements as "Open Questions"
- →The skill focuses on generating FSDs from PRD requirements
How it compares
This skill automatically generates a structured FSD with precise language and specific sections like atomic business rules and traceability matrices, unlike manually drafting a document.
Compared to similar skills
FSD Generator side by side with the closest alternatives in the catalog.
| Skill | Installs | Updated | Safety | Difficulty |
|---|---|---|---|---|
| FSD Generator (this skill) | 0 | 5mo | No flags | Intermediate |
| pmbok-project-management | 38 | 9mo | No flags | Intermediate |
| project-planner | 32 | 10mo | Review | Intermediate |
| spec-kit-workflow | 11 | 8mo | No flags | Intermediate |
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