Functional Specification Document (FSD) Template

Use this template to document detailed functional requirements for any feature.

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Document Control

Field	Value
Document Owner	[Your Name, Role]
Feature Name	[Feature Name]
Version	[1.0]
Status	[Draft / Under Review / Approved]
Last Updated	[Date]
Related BRD	[Link to BRD if applicable]
Related User Stories	[US-XXX, US-YYY]

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1. Executive Summary

[2-3 sentences describing what this feature does and why it's being built]

Business Justification:
[Why are we building this? What problem does it solve?]

Success Metric:
[How will we measure success? e.g., "Reduce cancellation rate from 15% → 10%"]

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2. User Stories

Primary User Story

[US-XXX]: As a [persona], I want [goal], so that [benefit].

Acceptance Criteria:

• GIVEN [precondition]
  WHEN [action]
  THEN [expected result]

• GIVEN [precondition]
  WHEN [action]
  THEN [expected result]

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Secondary User Stories (if applicable)

[US-YYY]: [Story text]

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3. Functional Requirements

FR-001: [Requirement Title]

Description: [What the system must do]

Preconditions:

• [Requirement 1]
• [Requirement 2]

Flow:

1. [Step 1]
2. [Step 2]
3. [Step 3]

Business Rules:

• [Rule 1]
• [Rule 2]

Error Handling:

• IF [error condition] THEN [behavior]

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FR-002: [Requirement Title]

[Repeat structure as needed]

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4. User Interface Specifications

Screen 1: [Screen Name]

Trigger: [How user gets to this screen]

Elements:

Wireframe:

┌─────────────────────────────────────┐
│  [Screen Title]                     │
├─────────────────────────────────────┤
│                                     │
│  [Element placeholder]              │
│                                     │
│  [Button: Action Label]             │
│                                     │
└─────────────────────────────────────┘

Validation Rules:

• [Field]: [Validation rule]

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5. API Specifications

Endpoint: [HTTP Method] [Path]

Purpose: [What this endpoint does]

Request:

[HTTP Method] /api/v1/[resource]
Content-Type: application/json
Authorization: Bearer {token}

{
  "field1": "value1",
  "field2": "value2"
}

Response (Success):

{
  "id": 123,
  "status": "success",
  "data": {}
}

Error Responses:

Code	Condition	Response
400	Invalid input	{"error": "validation_error", "message": "..."}
404	Not found	{"error": "not_found", "message": "..."}
500	Server error	{"error": "internal_error", "message": "..."}

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6. Business Logic

Rule 1: [Rule Name]

IF [condition]:
    THEN [action]
ELSE:
    [alternative action]

Example:

def calculate_deposit(party_size, deposit_per_person=10):
    if party_size >= 6:
        return (party_size - 5) * deposit_per_person
    return 0

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7. Data Requirements

Database Changes

New Tables:

Modified Tables:

• Table name: Add column [column_name] ([type])

Sample Query:

SELECT * FROM [table] WHERE [condition];

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8. Edge Cases & Error Handling

Scenario	System Behavior
[Edge case 1]	[How system handles it]
[Edge case 2]	[How system handles it]
[Error condition]	[Error message and recovery]

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9. Non-Functional Requirements

Performance

• [Page load time < X seconds]
• [API response < X ms]

Security

• [Authentication required]
• [Data encryption requirements]

Accessibility

• [WCAG compliance level]

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10. Testing Requirements

Test Cases

ID	Scenario	Expected Result
TC-001	[Happy path]	[Success behavior]
TC-002	[Edge case]	[Expected handling]
TC-003	[Error case]	[Error message shown]

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11. Dependencies

Dependency	Team	Status	Notes
[What you need]	[Who provides it]	[Status]	[Additional info]

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12. Open Questions

1. Question: [What needs to be decided?]
   Options: [A, B, C]
   Recommendation: [Your suggestion]
   Decision Owner: [Who decides]
   Deadline: [By when]

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13. Rollout Plan

Phase 1: [Internal Beta]

• [Details]

Phase 2: [Limited Release]

• [Details]

Phase 3: [Full Launch]

• [Details]

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14. Approval

Role	Name	Signature	Date
Product Manager
Engineering Lead
QA Lead

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