# Build your own CUSTOM API MCP server with Google Sheets: n8n workflow

> Started by an event in a connected app, and works across Google Sheets. 20 steps, 2 branches: a working afternoon to understand properly.

Source: https://millionrounds.com/workflow/build-your-own-custom-api-mcp-server-with-google-sheets (Millionrounds; every figure on the page links to its filing or article)

[Automation library](https://millionrounds.com/workflows) · [Setup and learning](https://millionrounds.com/workflows?category=Setup+and+learning#library)

# Build your own CUSTOM API MCP server with Google Sheets

Started by an event in a connected app, and works across Google Sheets. 20 steps, 2 branches: a working afternoon to understand properly.

Medium

[Download free](https://millionrounds.com/login?next=%2Fapp%2Fworkflow%2Fbuild-your-own-custom-api-mcp-server-with-google-sheets)

**20 steps** Medium: a working afternoon

**2** Branches: places the flow splits

**0** Loops or waits

**1** Service it connects to

## The flow

Starts it 2 Model 3 Logic 11 Service 4

The steps in the order they run, from what starts it.

- 1 **When Executed by Another Workflow** Execute Workflow trigger *Starts it*
- 2 **Update Employee** Tool Workflow *Model*
- 3 **Get Employee** Tool Workflow *Model*
- 4 **Search Employees** Tool Workflow *Model*
- 5 **Log Call** Google Sheets *Service*
- 6 **Paycaptain MCP Server** Mcp trigger *Starts it*
- 7 **Operation** Switch *Logic*
- 8 **Get Employees** Http Request *Service*
- 9 **Get Employees1** Http Request *Service*
- 10 **Valid Fields Only** Set *Logic*
- 11 **Filter Matches** Filter *Logic*
- 12 **Filter Matching ID** Filter *Logic*
- 13 **Has Valid Request?** If *Logic*
- 14 **Strip Sensitive Fields** Set *Logic*
- 15 **Strip Sensitive Fields1** Set *Logic*
- 16 **Update Employee1** Http Request *Service*
- 17 **Get Error Response** Set *Logic*
- 18 **Aggregate Search Results** Aggregate *Logic*
- 19 **Aggregate Get Response** Aggregate *Logic*
- 20 **Get Success Response** Set *Logic*

## How it's built

- **Starts on:** An event in a connected app
- **Steps:** 20, with 2 branches
- **Size:** Medium: a working afternoon
- **Connects to:** Google Sheets
- **Model:** None. This is plumbing, not judgement

## Questions

What does it need to run?

An n8n account, plus your own Google Sheets account. You connect your own accounts after importing it; none are included.

What starts it?

It starts on an event in a connected app.

Does it use AI?

No. Every step is fixed logic or a call to a service, so it does the same thing every time.

How long does it take to set up?

Plan an afternoon. 20 steps is enough that you should read each one before running it.

How do I import it?

Copy the workflow, open a new workflow in n8n and paste. The steps appear on the canvas, ready for your own accounts.

**Before you run it**

Nothing here has been tested by us. It is somebody's working automation, read and described from its own steps. Treat the connections it wants as a list of accounts it will touch, and read the 20 steps before you point it at anything that matters.

## Run it in n8n

- **Create your n8n account** Free to start. n8n is where the workflow runs. [Create an n8n account ↗](https://millionrounds.com/n8n)
- **Download the workflow** Free with a Millionrounds account. [Download free](https://millionrounds.com/login?next=%2Fapp%2Fworkflow%2Fbuild-your-own-custom-api-mcp-server-with-google-sheets)
- **Paste it into n8n** Open a new workflow in n8n and paste. Then connect your own accounts.

Stored with the author's traces removed: canvas notes, instance identifiers, saved credential names and any live document they had left behind.

## Connects to

Each opens the other workflows that use it.

[Google Sheets](https://millionrounds.com/workflows?service=Google+Sheets#library)

## Workflows like it

Also setup and learning, with the same services where possible, closest in size first.

- [**Expose CRM read/write tools to Claude and ChatGPT with Gmail** 18 steps · Gmail, Google Sheets](https://millionrounds.com/workflow/expose-crm-read-write-tools-to-claude-and-chatgpt-with-gmail)
- [**Freelancer Client Onboarding Automation - n8n Workflow Template** 17 steps · Airtable, Gmail](https://millionrounds.com/workflow/freelancer-client-onboarding-automation-n8n-workflow-templat)
- [**Search Slack for n8n templates with OpenAI and Google Sheets** 23 steps · Google Sheets, Slack](https://millionrounds.com/workflow/search-slack-for-n8n-templates-with-openai-and-google-sheets)
- [**Investigate phishing emails from Google Sheets with MCP** 13 steps · Google Drive, Google Sheets](https://millionrounds.com/workflow/investigate-phishing-emails-from-google-sheets-with-mcp)
- [**AI Agent to send Emails from Google Sheets (video tutorial)** 9 steps · calls a model · Gmail, Google Sheets](https://millionrounds.com/workflow/ai-agent-to-send-emails-from-google-sheets-video-tutorial)
- [**Automated export of Quickbooks Online data with Google Sheets** 4 steps · Google Sheets](https://millionrounds.com/workflow/automated-export-of-quickbooks-online-data-with-google-sheet)