Quickstart

Three steps: get an API key, add the MCP server to your client, and ask your agent to fill a form.

Before you start

A fenfill workspace on Pro or above. Compare plans.
Node.js 22 or newer (npx comes with it).
An MCP client: Claude Code, Claude Desktop, Cursor, or any client that can launch a local (stdio) server.

1. Create an API key

In fenfill, open Settings → API keys and choose Create key. Give it a name you'll recognise, like the machine or the agent that will use it.

The key starts with ff_live_ and is shown once. Copy it now. We store only a hash, so we can't show it again. If you lose it, revoke it and create a new one.

2. Add the MCP server to your client

Run this in a terminal.

Terminal

claude mcp add fenfill --scope user -e FENFILL_API_KEY=ff_live_… -- npx -y @fenfill/mcp

Add this to claude_desktop_config.json, then restart Claude Desktop.

JSON

{  "mcpServers": {    "fenfill": {      "command": "npx",      "args": ["-y", "@fenfill/mcp"],      "env": { "FENFILL_API_KEY": "ff_live_…" }    }  }}

Add this to ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (one project).

JSON

{  "mcpServers": {    "fenfill": {      "command": "npx",      "args": ["-y", "@fenfill/mcp"],      "env": { "FENFILL_API_KEY": "ff_live_…" }    }  }}

Any client that launches a stdio server: run this command with FENFILL_API_KEY in its environment.

Terminal

FENFILL_API_KEY=ff_live_… npx -y @fenfill/mcp

Check it works: ask your agent to run get_account. It answers with your plan and the page scans you have left.

3. Fill your first form

Give your agent a blank PDF and what to put in it. For example:

Prompt

Fill ~/Downloads/fw9.pdf for Acme Ltd, an LLC taxed as an S corporation, at 1 Main St, Springfield. Save it as ~/Downloads/fw9-acme.pdf.

The agent will:

call analyze_form on the blank PDF. The W-9 already has fillable fields, so it is read directly, with no AI, and uses no page scans;
read the fields it gets back and match your details to them;
call fill_form with the answers. The MCP server writes a new, flattened PDF on your machine and never sends the answers anywhere.

Want to check the result? Ask the agent to run preview_page. It draws the page on your machine with every field outlined and tagged.

What it costs

Analyzing a flat or scanned form uses one page scan per analyzed page, from your plan.
Forms that already have fillable fields use none, unless you opt in to detect_extra_blanks, which uses one page scan per analyzed page.
Analyzing the same file again comes from the local cache and uses none. force: true analyzes it again and uses scans again.
Filling never uses page scans.
To check before you spend, call analyze_form with estimate: true. It counts pages and spots fillable fields on your machine, uploads nothing, and returns the estimated scans.

How many scans each plan includes is on the pricing page.

MCP server: all settings, every client, troubleshooting.
Tools: all 13 tools, including templates, fillable PDFs, recipient links and layout fixes.
What is sent where: the full data table and the local cache.
API: call /v1 directly.