MCP servers
Add any MCP server that speaks HTTP, store its token, and pick which tools a step may call.
A Tool call or Agent step can use any server that speaks MCP over HTTP, in addition to the built-in connectors.
Adding a server
Open the step
Select a Tool call step or an Agent step. Under Custom MCP, choose Add server.
Enter the server
Give it a name and its URL, for example https://example.com/mcp.
If the server needs a bearer token, paste it in the token field. It is encrypted before it is stored, and the form never shows it again.
Save
Flowblocks calls the server and lists its tools before anything is stored. A server that cannot be reached is not saved.
Pick tools
Choose the server on the step, then choose which of its tools the step may call.
You can save up to 20 servers.
Changing a token
Open the server and paste a new token to replace the stored one. Leave the field blank to keep it, or clear it to remove it.
Which URLs are allowed
In production a server URL must be https and must resolve to a public address. Loopback, private ranges and link-local addresses are rejected.
Local development allows http and private hosts. If a deployed, self-hosted install needs to reach a server on a private network, set MCP_ALLOW_PRIVATE_URLS=true.
An MCP server's tools can do whatever that server allows, including writing and deleting. Give a step only the tools it needs, and put approval in front of the ones that change things.
From Ask AI
If a prompt to Ask AI names an MCP URL, it registers the server for you and links it to the Tool call step it adds.