Custom GPT: Build a Bid Writing Assistant for Your Company

What This Builds

You'll build a Custom GPT that knows your company's standard bid language, your typical scope inclusions and exclusions by project type, your tone and format preferences, and your most common bid writing tasks. Instead of re-explaining your context every conversation, the GPT starts with all of that already loaded. Your estimating team can share it, so your scope letters, cover letters, and PM handoffs all have a consistent voice, even across estimators.

Prerequisites

• ChatGPT Plus subscription ({{tool:ChatGPT.price}}; Custom GPTs require Plus or higher)
• 30-60 minutes to write your system instructions
• Optional: a few example documents to upload as reference (past scope letters, cover letters)

The Concept

A Custom GPT is like hiring an assistant who's already been trained on your company's style guide, your standard scope language, and your bid document preferences before you ever open a conversation. You set it up once, and then every estimator on your team starts from that shared baseline instead of explaining everything from scratch.

Think of it like setting up a template in Word, but instead of a document template, it's a conversation template that adapts to each specific bid.

Build It Step by Step

Part 1: Access the Custom GPT Builder

1. Log in to ChatGPT at {{tool:ChatGPT.url}}
2. In the left sidebar, click Explore GPTs (or look for a "+" next to "My GPTs")
3. Click Create in the top right corner
4. You'll land on the GPT builder with two panels: a chat on the left (to configure via conversation) and a preview on the right

What you should see: The builder interface with a "Create" tab and a "Configure" tab. Start with Configure for more control.

Part 2: Write Your System Instructions

Click the Configure tab. This is where you define what your GPT knows and how it behaves. In the Instructions box, write your system prompt. Here's a template to customize:

You are a bid writing assistant for [Your Company Name], a commercial general contractor based in [Location] specializing in [Project Types].

Your role: Help estimators write professional, precise bid documents (scope letters, cover letters, PM handoff memos, subcontractor follow-up emails, and addendum responses).

Company voice: Direct, professional, and specific. No filler phrases. No vague language. Every document should be actionable and clear.

Standard inclusions for GC scope letters (unless told otherwise):
- Project supervision and general conditions
- Temporary facilities (fencing, power, water, toilets) unless owner-provided
- Coordination of all subcontractors
- Safety compliance per OSHA and local requirements
- Project schedule and progress reporting

Standard exclusions (unless told otherwise):
- Hazmat abatement unless shown on drawings
- Owner-furnished equipment
- Permit fees over $[amount] (carried separately)
- Furniture, fixtures, and equipment (FF&E)
- Testing and inspection fees (carried as allowance unless specified)

When writing scope letters:
1. Address to the specific trade
2. Include project name, scope description, relevant spec sections, and bid deadline
3. List inclusions and exclusions as numbered bullets
4. End with clear submission instructions

When writing cover letters:
1. Open with project name and our firm's relevant experience
2. Summarize our approach and key qualifications
3. List major scope assumptions and exclusions
4. Close with a clear next step

When writing PM handoff memos:
1. Use memo format: To, From, Date, Project, Re
2. Cover: budget basis, scope boundaries, key sub notes, known risks, bid-day decisions
3. Flag anything that was verbally agreed but not in writing

Customize every bracketed item to match your actual company.

Part 3: Set the GPT Name and Description

1. At the top of the Configure tab, enter a Name: "Bid Writer: [Your Company]"
2. Write a Description: "Writes scope letters, cover letters, PM handoffs, and sub follow-ups using [Company]'s standard language and format."
3. Set a Conversation Starter (a prompt that appears when someone opens the GPT): "What document do you need? (scope letter, cover letter, PM handoff, sub follow-up, addendum response)"

Part 4: Upload Reference Documents (Optional but Valuable)

In the Knowledge section, you can upload files your GPT can reference:

1. Click Upload files
2. Upload 2-3 example scope letters you're happy with
3. Upload an example cover letter and PM handoff memo
4. Consider uploading your standard terms and conditions boilerplate

What this does: The GPT will match the style, format, and language patterns from your example documents automatically.

Part 5: Test and Refine

Before sharing with your team, test the GPT:

1. Click the Preview panel or click Save and open the GPT
2. Ask it to write a scope letter for a fictional project
3. Check: Does it use your company's standard inclusions/exclusions? Is the format correct? Is the tone right?
4. Go back to Configure and adjust the instructions for anything that's wrong

Repeat until 3 consecutive test outputs require minimal editing.

Real Example: Setting Up for Healthcare Projects

Setup: Your company focuses on healthcare construction. You add to your system instructions:

For healthcare projects, always include in scope letters:
- Infection control protocols (ICRA compliance)
- After-hours work requirements for occupied facilities
- Coordination with hospital facilities team
- Interim life safety measures (ILSM) if applicable
Standard exclusion for healthcare: Medical equipment (owner-furnished, installed by vendors)

Input: An estimator types: "Write a scope letter for an electrical sub on a 45,000 SF hospital wing renovation, occupied facility, bid due Friday."

Output: A scope letter that automatically includes ICRA coordination requirements, ILSM mention, after-hours work clause, and excludes medical equipment, without the estimator having to remember or type any of it.

Time saved: 20 minutes of manual scope letter writing → 3 minutes of review and send.

What to Do When It Breaks

• GPT uses wrong inclusions/exclusions → Edit your system instructions to be more specific. Add "Always include X unless the estimator says otherwise" for items that keep getting missed.
• Tone is too formal or too casual → Add example sentences in your instructions: "Write in the style of this sentence: [paste example]"
• GPT makes up scope items not in your instructions → Add "Only include scope items the estimator explicitly mentions or that are in your standard inclusions list. Do not add items not requested."
• File uploads aren't reflected in output → Check that the Knowledge section shows the files as uploaded. Try re-uploading if they don't appear.

Variations

• Simpler version: Skip the file uploads and just use the system instructions. Most of the value comes from the instructions, not the uploaded examples.
• Extended version: Create separate GPTs for different project types (Healthcare GPT, Office GPT, Warehouse GPT), each with project-type-specific scope language and examples.

What to Do Next

• This week: Build the GPT and test it on your next 3 bid documents. Edit the instructions based on what needs fixing.
• This month: Share the GPT link with your estimating team. Collect feedback on what's missing or wrong and update the instructions.
• Advanced: Add a GPT for subcontractor quote leveling that understands your standard project types and flags gaps automatically.

Advanced guide for construction cost estimator professionals. These techniques use more sophisticated AI features that may require paid subscriptions.