Claude fill PDF: Instafill.ai MCP integration

Use Claude to fill out PDF forms directly from the chat. Connect Instafill.ai to Claude.ai, Claude Desktop, or Claude Code CLI and ask Claude to find, fill out, and download your forms - without leaving the conversation.

What This Integration Does

If you have ever searched for how to fill out a PDF with Claude, this is the answer. Instafill.ai connects to Claude through MCP (Model Context Protocol) - an open standard that lets AI assistants securely access external tools and data. Once connected, Claude has direct access to your Instafill.ai workspace: your forms, your fill history, predefined profiles, etc.

Instead of opening a PDF manually, copying field names, and entering data by hand, you describe what you need in plain language and Claude handles the rest. You can fill out PDF forms with Claude AI across three clients - Claude.ai (web and mobile), Claude Desktop (Windows and macOS), and Claude Code CLI.

Once connected, you can ask Claude things like:

• "I want to upload a new form"
• "Show me all forms available in my workspace"
• "Fill out the CMS-1500 claim form with my patient's information"
• "Find the prior authorization form and fill it out using my saved profile"
• "Download the completed form from my last session"

Claude finds the right form, fills it out using the data you provide, sources attached or saved profiles, and returns a download link when it is done.

Before You Start

You need:

• A Claude account - Claude.ai, Claude Desktop, or Claude Code CLI
• An Instafill.ai account - you can create one for free during the setup flow

No developer mode required. No extra configuration needed.

Setup: Choose Your Claude Client

Option 1 - Claude.ai (Web and Mobile)

Best for: everyday form filling tasks, users who work in a browser or on mobile, and teams that do not want to install additional software.

Steps:

1. Go to claude.ai/customize/connectors
2. Click the + icon, then click Add custom connector
3. In the "Remote MCP server URL" field, enter: https://api.instafill.ai/mcp
4. Save the connector and click Connect
5. Sign in to your Instafill.ai account, select your workspace, and approve permissions

The connection is live. Go back to any Claude.ai conversation and start asking questions.

Option 2 - Claude Desktop

Best for: users who prefer a native desktop application, workflows that involve local files, and anyone who wants Instafill.ai accessible without keeping a browser tab open.

Claude Desktop is Anthropic's standalone application for Windows and macOS. Connecting Instafill.ai to Claude Desktop means you can fill out PDF forms from your desktop environment - particularly useful if you are already working with local PDF files and do not want to switch to a browser.

Steps:

1. Open Claude Desktop and navigate to Settings > Connectors
2. Click Add Custom Connector
3. In the "Remote MCP server URL" field, enter: https://api.instafill.ai/mcp
4. Click Connect and follow the OAuth flow to sign in to your Instafill.ai account
5. Select your workspace and approve permissions

Once connected, Instafill.ai tools are available in all your Claude Desktop conversations.

Full instructions are in the Instafill.ai MCP Server Documentation.

Option 3 - Claude Code CLI

Best for: developers, technical teams, and anyone who wants to automate form filling as part of a larger workflow or integrate it into scripts and pipelines.

Claude Code is Anthropic's command-line tool for working with Claude in a terminal environment. Connecting Instafill.ai to Claude Code lets you trigger form fill jobs programmatically, chain them with other operations, and build automated document workflows without a graphical interface.

This is the right option if you want to do things like:

• Automatically fill out forms as part of a data processing pipeline
• Integrate Instafill.ai into a development or deployment workflow
• Run batch fill jobs from the terminal without opening a browser
• Test and build custom integrations against the Instafill.ai MCP tools

Steps:

1. Install Claude Code CLI if you have not already - see the Claude Code documentation
2. Run this command in your terminal:

   claude mcp add --transport http instafill https://api.instafill.ai/mcp
   

3. Launch Claude Code in your project directory:

   claude
   

4. Use the /mcp command to view connected MCP servers and authenticate:

   /mcp
   

5. Select "Authenticate" when prompted and complete the OAuth flow in your browser

Once authenticated, Instafill.ai tools are available through natural language inside Claude Code, just like in Claude.ai.

How to Fill Out PDF Forms with Claude

Once the connector is active, filling out a PDF form is a conversation. Here are some examples of how to use it.

Browse your forms:

"List all my forms" "Find the I-9 form" "Show me all my filled forms from this week"

Fill out a form:

"Fill out the prior authorization form with the following patient details: ..." "Fill out the CMS-1500 form using my saved profile for Dr. Smith's practice"

Claude fills out the form using the data you provide in the conversation. Your data goes directly to Instafill.ai servers - it is not stored in your Claude conversation history.

Track and download:

"Is my form ready?" "Download the completed form"

Claude checks the status and returns a download link when the fill is complete. Download links are valid for 10 minutes.

Manage profiles:

"Create a new profile" "Show me my saved profiles"

What Claude Can Do with Your Instafill.ai Workspace

The integration gives Claude access to 20 tools across your workspace:

The table above shows the most common actions. The full set of 20 tools also covers details like reading back the structured field data from a completed form, searching forms by name, setting which fields depend on others, and managing profile files and text.

New in the Latest Update

The MCP integration was rebuilt, and three new capabilities are worth calling out, because they let Claude do things that previously required the Instafill.ai web app.

Inspect a form's fields (get_form_fields). Ask Claude to pull the full field structure of any form - field names, descriptions, control types, and dependencies - right in the chat. This is handy when you need to understand how a form is built, or when you want to use the field setup of one form to help fill another.

"Show me all the fields on the CMS-1500, with their groups and dependencies"

Edit a form's fields (update_form_fields). This is our Field editor, but in the chat. Field editor lets you correct how the AI reads a form - renaming a field, changing its type, adjusting its description, grouping it, or marking it to be skipped - so future fills come out right. Now you can ask Claude to make those same changes in plain language, and they are saved to the form and reflected in your workspace, exactly as if you had edited them in the web app.

"Rename the 'Addr 1' field to 'Street address', and exclude the office-use-only fields from filling"

Reuse the inputs from a past fill (get_fill_inputs). Claude can retrieve the source data you used on an earlier fill - files, text, and profiles - so you can re-run a fill or apply the same inputs to another form without re-entering anything.

"Pull the inputs from my last fill and use them to fill this updated version of the form"

See It in Real Sessions

The three capabilities above are easier to show than explain. Each link below opens a full Claude Code session where Claude inspects a form, corrects how a field is read, and refills it, all over MCP. Nothing to install - just open and read.

• Fixing a mis-formatted phone field by asking - A CMS-1500 phone number came out as 5,550,192. Claude finds the field, switches its type, adds a format example, and refills, all in chat.
• Filling an ABA form from a saved profile - A 1199SEIU authorization form filled from a profile, with signature fields excluded and a failed fill retried using the same data.

Use Cases

ABA Therapy and Behavioral Health

ABA practices deal with high documentation volume every day - session notes, progress reports, prior authorizations, CMS-1500 claims, and insurance packets. Most of these are the same forms filled out with different client data each time.

With Claude connected to Instafill.ai, a BCBA or office staff member can paste session notes directly into the chat and ask Claude to fill out the right form from them. No switching between the patient record, the PDF, and the billing system - everything happens in one conversation.

For example:

"Here are today's session notes for patient John D. Fill out the CMS-1500 claim form using this information: [type or paste notes]"

Claude fills out the form and returns a download link in seconds.

Healthcare and Medical Practices

Credentialing packets are one of the most time-consuming forms of paperwork in healthcare - the same provider information repeated across 20 to 30 pages for different insurers or facilities.

With Instafill.ai, you upload the provider's CV, license documents, and any supporting files once. Then ask Claude to fill out the credentialing packet using those uploaded documents as the source. It reads across multiple file formats - PDF, DOCX, TXT - and maps the right information to the right fields automatically.

"Fill out the CAQH credentialing form using the documents I just uploaded"

Legal Practices and Immigration Attorneys

Immigration attorneys work with the same client data across multiple USCIS forms - I-485, I-131, I-765, G-1145 - often in the same case. Rather than re-entering the same information for each form, staff can upload the client's source documents once and ask Claude to fill out each form from them in sequence.

"Fill out form I-765 using the client intake document I uploaded"

The same uploaded source works across multiple fill jobs. No re-uploading, no re-entering.

HR and Operations Teams

Onboarding paperwork involves forms that rarely change but need to be filled out fresh for every new hire. HR staff can type the employee's details directly into the Claude conversation and ask Instafill.ai to fill out the relevant forms on the spot - I-9 verifications, state tax forms, direct deposit authorizations - without building any templates or profiles in advance.

"New hire: Jane Smith, SSN ending 4521, start date May 1. Fill out the I-9 and the state withholding form"

Construction and Contracting

Prequalification packets and subcontractor agreements often run to dozens of pages. Rather than filling them out manually or maintaining templates, project teams can upload the company's existing capability statement or past project list as a source document and ask Claude to fill out any new prequalification form from it.

"Fill out this prequalification packet using our company capability statement PDF"

The source document stays on file in Instafill.ai and can be reused for every new packet that comes in.

How Claude Differs from ChatGPT for PDF Form Filling

Both Claude and ChatGPT connect to the same Instafill.ai MCP server and have access to the same 20 tools. The main difference is how you provide your form data:

• With Claude - you provide your data directly in the conversation. Claude reads it and passes it to Instafill.ai. This makes the flow faster and more conversational.
• With ChatGPT - data is entered through a secure widget that opens outside the chat. This keeps the data out of the conversation history, which some users prefer for sensitive information.

Both approaches are secure. Your data is transmitted directly to Instafill.ai servers and is not retained by either AI assistant.

If you want to connect ChatGPT instead, see Connect Instafill.ai to ChatGPT with MCP.

Common Questions