Custom AI Writing Assistant: Build a Firm-Specific Paralegal Assistant

What This Builds

Instead of starting every AI session with a blank slate and re-explaining your firm's style, practice areas, and preferences, this builds a Claude Project — a persistent AI workspace that already knows your firm's templates, writing standards, and the attorneys you support. Every drafting conversation starts from shared context. Documents come back in your firm's style, not generic AI style.

Prerequisites

• Claude Pro account ($20/month at claude.ai)
• 30–60 minutes to collect and paste in firm templates and style guidance
• Approval from supervising attorney to include non-privileged firm templates in the project

The Concept

A Claude Project is like having a dedicated assistant who has read your firm's entire style guide, learned your standard templates, and knows which attorney is fussy about what. You set it up once by giving it your templates and instructions. Then every conversation in that Project starts from that foundation. You're not re-explaining your firm's letter format every time — the Project already knows it.

Think of the difference between training a new temp who knows nothing about your firm vs. a seasoned paralegal who knows exactly how Partner A likes briefs formatted and which client always needs extra hand-holding in their letters.

Build It Step by Step

Part 1: Create the Project

1. Log in to claude.ai (Pro account required)
2. In the left sidebar, click "+ New Project"
3. Name it something specific: "Smith & Jones LLP — Paralegal Assistant" or "[Firm Name] Legal Drafting"
4. Click "Create Project"

What you should see: A new project workspace with a "Project instructions" section and a document upload area.

Part 2: Write the Project Instructions

Click "Edit project instructions" and write a system prompt that tells Claude exactly who it is and how to behave. Copy and customize this template:

You are a legal drafting assistant for [Firm Name], a [practice area] law firm based in [city, state].

YOUR ROLE:
- Help paralegals draft, revise, and organize legal documents
- Follow the firm's formatting and style standards at all times
- Use formal legal language appropriate for [practice area] practice
- Never fabricate case citations or legal authority — only use citations the paralegal provides

FIRM STYLE STANDARDS:
- Letter format: [describe your firm's letter format — address block location, date format, Re: line, salutation style]
- Document headings: [ALLCAPS centered / bold sentence case / etc.]
- Tone: [formal and professional / warm and approachable with clients]
- Citation format: [Bluebook / state-specific citation style]
- Signature line: [how your firm formats attorney signatures]

ATTORNEYS YOU SUPPORT:
- [Attorney 1 name]: Prefers [brief notes on their style — "concise, no passive voice", "always include case caption in letters", etc.]
- [Attorney 2 name]: Prefers [style notes]

PRACTICE AREAS THIS FIRM HANDLES:
[list the practice areas — e.g., personal injury, business litigation, estate planning, family law]

IMPORTANT LIMITS:
- Do not provide legal advice or suggest strategy — that is the attorney's role
- Do not generate case citations — the paralegal provides all verified citations
- Always flag when a document needs attorney review before use
- If asked to draft something outside the firm's typical work, note that it's outside your context

Click "Save instructions."

Part 3: Upload Firm Templates and Reference Documents

In the Project's document section, click "Upload" and add:

• Your firm's standard letter template (Word → converted to text, or paste the text)
• Standard opening and closing paragraph language for each document type
• A sample demand letter (redacted of identifying information)
• A sample client intake summary
• A list of the firm's standard objections language (you can generate this with the Level 1 prompt guide)

These documents become the AI's reference library. When you ask Claude to draft a letter, it will automatically match the style and structure of what you uploaded.

What you should see: Documents listed in the Project's knowledge base.

Part 4: Test and Refine

Start a new conversation within the Project. Test with a real task:

• "Draft a cover letter to accompany document production in the [case type] format"
• "Write a client update email for a personal injury client about a deposition scheduled next week"

Compare the output to your firm's actual style. If something is off, go back to the Project instructions and add more specific guidance. Iteration improves quality quickly — most Projects reach good output quality after 2–3 refinement cycles.

Real Example: Firm-Specific Style in Action

Setup: A mid-size personal injury firm has loaded its standard templates and written instructions for two attorneys: Partner A (concise and direct, no passive voice) and Associate B (thorough, includes client-education sections in every letter).

Input: "Draft a client update letter for [client name] regarding their personal injury matter. The case is in discovery, opposing counsel just served requests for production, and we need responses in 30 days. Write this for Partner A."

Output: A concise, direct letter in the firm's exact format — no fluff, clear action required, exactly matching Partner A's style. The paralegal makes minor factual edits and submits for signature.

Without the Project: The paralegal would need to specify all style requirements in every new conversation, often getting generic output that requires significant editing.

Time saved: 15–20 minutes of editing on every drafted document.

What to Do When It Breaks

• Output doesn't match firm style → Add more specific examples to the Project instructions — paste 2–3 sentences of "good" output and say "match this tone and structure"
• Claude forgets attorney preferences → Move attorney preferences to the top of the system prompt, not the bottom — earlier instructions carry more weight
• Document upload isn't being used → Reference it explicitly in your prompt: "Using the demand letter template in this Project's knowledge, draft a demand letter for..."
• System prompt getting too long and confused → Split into two Projects: one for litigation drafting, one for transactional/contract work

Variations

• Simpler version: Instead of a full Project, start every Claude conversation by pasting a short "context block" (your firm's 5-bullet style guide). Less powerful but no setup required.
• Extended version: Create separate Projects for each practice area (one for PI litigation, one for corporate matters) with specialized templates and language for each

What to Do Next

• This week: Build the Project, test with 3–4 document types
• This month: Add templates for every document type you regularly draft; refine instructions based on attorney feedback
• Advanced: If your firm uses Microsoft Teams or Slack, explore whether the Claude API can be connected to post summaries or draft responses directly in those channels (requires IT involvement)

Advanced guide for paralegal professionals. Claude Projects require a Claude Pro subscription. Never upload client-identifying information or privileged communications into AI systems without your firm's written AI policy approval.