A practical example of how clear IT documentation streamlines real-world 3PL system integrations.
Intro
Imagine you’re running a busy 3PL warehouse. You’re using OpenBoxes to manage inventory and warehouse operations (WMS), and ShipStation to handle shipping labels and carrier selection (TMS). But here’s the catch: these systems aren’t talking to each other. Orders are entered manually, data gets copied and pasted between systems, and teams spend hours chasing status updates. Mistakes happen, and customers get frustrated.
This blog is part of our “IT Docs That Actually Help” series, created for developers, business analysts, PMs, and stakeholders working on real-world IT projects, especially in logistics, warehousing, and supply chain environments. Today we’re covering the Functional Specification — a document that acts as the detailed blueprint between the “what” of business goals and the “how” of technical implementation.
If you’re building a web app or integration between WMS and TMS systems, or any two platforms like ERP, IMS, OMS, and TMS, a good Functional Spec can be the difference between a working MVP and a failed project. Let’s dig in.
What Is a Functional Specification?
A Functional Specification (or Functional Spec) is a document that clearly describes how a system or integration should behave from a user’s perspective. It outlines the system’s features, user interactions, business rules, and expected outputs — all in clear, non-code language.
It’s not the same as:
A Business Requirements Document (BRD) – which focuses on what the business needs.
A Technical Specification – which goes deep into how the system will be engineered (code, architecture, data structures).
A UI Wireframe – which only shows screen layout or design ideas.
Instead, the Functional Spec acts as the bridge between your BRD and your dev team’s first commit.
When and Why to Use It
You’ll want a Functional Spec right after the BRD is approved and before your developers start writing serious code.
Why it’s useful:
Clarifies scope before dev starts
Reduces the risk of rework or missed features
Helps get early stakeholder alignment
Documents edge cases and logic that would otherwise live in someone’s head
Without it:
Developers build based on assumptions
QA testers don’t know what “correct” behavior looks like
PMs get scope creep and misaligned timelines
Business users keep saying “That’s not what I meant!”
Who Owns the IT Functional Specification?
Ownership depends on your team setup, but here’s a good breakdown:
Primary Author: Usually a Business Analyst (BA) or Product Manager (PM)
Technical Contributors: Developers, Architects, or Tech Leads
Business Reviewers: Stakeholders, Operations Managers, 3PL leads
Approver: PM or Project Sponsor
Everyone should have a chance to review and flag questions.
✅ What to Include:
Overview / Purpose
Functional Requirements (in bullet format)
User Stories or Scenarios
Business Rules
Field definitions
External System Interactions (API, triggers)
Screenshots or Wireframes (if UI is involved)
Assumptions
Edge Cases and Error Handling
❌ What NOT to Include:
Actual code
Low-level technical decisions (e.g. database schema)
API syntax or architecture details (belongs in the Tech Spec)
UI design mockups (wireframes are okay)
How to Get Started Writing One
Start by gathering answers to these questions:
What is the user trying to do?
What steps do they take?
What should happen at each step?
What rules or validations apply?
What exceptions or errors might occur?
Draft these first:
A plain English purpose statement
1–3 key user stories
A bulleted feature list with requirements
Notes on external system behaviors
Common Starter Templates:
You can use Google Docs, Word, or tools like Confluence and Notion. Here’s a free starter template in markdown or PDF you can use (link below in Section 6).
Real Example + Downloads
Let’s go back to our 3PL use case.
Mickey’s Logistics uses OpenBoxes for WMS and ShipStation for TMS. They want a simple internal web app that:
Automatically pulls new outbound orders from OpenBoxes once marked “Ready to Ship”
Creates the corresponding shipment in ShipStation
Returns tracking numbers and carrier info to OpenBoxes
Download our Real IT Functional Specifications Example – OpenBoxes WMS to ShipStation (.docx)
- Download the Blank Functional Spec Template (.docx)
Conclusion
A Functional Specification isn’t a formality — it’s a powerful, collaboration-driven tool that saves time, prevents rework, and helps teams ship features that actually solve the right problems.
In fast-paced 3PL and logistics environments, especially when integrating WMS and TMS systems, solid documentation gives you the clarity to move faster — not slower.
Next up in our “IT Docs That Actually Help” series:
We’ll walk through how a Technical Specification takes your Functional Spec one step further — turning features into system architecture, API calls, and dev-ready tasks.
Until then, don’t stress about perfect documentation. Focus on useful documentation — the kind your team actually reads, uses, and builds from.
Want a custom version of this spec tailored to your 3PL? Reach out to our team — we love simplifying logistics through smart tech.