Connect an MCP server and call a tool
More and more services offer their functions as an MCP server (Model Context Protocol): a list of tools with a name, a description and arguments. Flow connects such a server as a connection; its tools become steps in workflows and tools for AI Colleagues. Tools that change something only work when the connection may write. You need: the MCP server's address (Streamable HTTP, usually ending in /mcp) and possibly a key.
Open your development environment
In the portal, under Environments, click Development, and there Open. Flow opens in a new tab and you are signed in straight away.
- Click Development
- Click Open ↗
Connect the MCP server
Under Connections choose MCP server. Fill in the address and the key; it is stored encrypted. Leave access on Read only: Flow may then only use tools the server marks as reading. Save and test makes contact straight away and counts the tools.
- Click Connections
- Click MCP server
- In Name, type
Bike rental · MCP - In **MCP server address ***, type
http://127.0.0.1:59249/mcp - In Key / token, type
••••••••
- Click Save and test
- Click Cancel
Call a tool in a workflow
Create a workflow and search the library for MCP. Choose MCP · Call tool and your connection. Under Tool click Pick…: Flow fetches the server's tools. Choose List bikes and give the arguments as JSON — here only e-bikes.
- Click Add to General
- Click New workflow
- In Workflow name, type
Available rental bikes
- Click Add node
- In Search a node, type
MCP
- Click Call tool
- In Connection, choose Bike rental · MCP · Read only
- Click Pick…
- Click Code
- In Arguments, type
{"type": "e-bike"}
- Click the dot of ‘Event trigger’
- Click the dot of ‘MCP · Call tool’
- Click the step ‘Event trigger’
- Click Align horizontally
- Click Save
Run and read the result
At the bottom you see that the step stored the tool's result. Under Data after the run you find it, ready for the next step.
- Click Run
A tool that changes something: refused
Now choose the tool Reserve bike. The server marks it as writing; because the connection may only read, Flow refuses the call before it reaches the server. Only when you set access to Read and write is it allowed.
- Click the step
- Click Pick…
- Click Save
- Click Run
This guide was carried out step by step on 22 Oct 2026 by an automated test on Flow (version 3e563176).