Create an MCP server with Postman Flows

Postman Flows empower you to create a Model Context Protocol (MCP) server using MCP tools and a Flows scenario. Once deployed, the action’s URL can receive requests, process incoming data using blocks and MCP tools, and send responses.

Create an action and a toolDefinition scenario

To begin building an MCP server in Postman Flows, do the following:

1. Create an action in Postman Flows.

2. In the action, create a scenario and name it "toolDefinition".

Add tools to the toolDefinition scenario

When creating an MCP server with an action in Postman Flows, you define the MCP tools in the action's scenario. To add MCP tools to a toolDefinition scenario, do the following:

1. In the Body section of your toolDefinition scenario, enter one or more tools using the MCP tool definition structure.

   Example:

   {
     "tools": [
       {
         "name": "greeter",
         "description": "Says hello to a person by their first name",
         "inputSchema": {
           "type": "object",
           "properties": {
             "first_name": {
               "type": "string",
               "description": "The person's first name"
             }
           },
           "required": [
             "first_name"
           ]
         }
       }
     ]
   }
   

2. Add blocks to the action to perform the tool's task.

   Example:

   

3. (Optional) For MCP servers that have multiple tools, you can use a Condition block to check which tool is being called in the request. Then a Select block can parse the tool's arguments.

   

4. Deploy the action. Users can send MCP requests to the deployed action's URL.

Send an MCP request to the server

When the tools are defined and the action is deployed, you can invoke the action with an MCP client or AI tool call. Use this input format to specify the tool and its parameters:

{
   "name": "<the tool's name>",
   "arguments": {
    "<parameter name>": "<parameter value>"
   }
}

To create an MCP request in Postman, do the following:

1. In the action, click Deploy.

2. Hover over the MCP URL and click Open in MCP request. A new MCP request opens. Alternatively, click the URL to copy it, then share it with a user.

3. In the MCP request, make sure HTTP is selected from the protocol dropdown list.

4. Click Connect. The MCP server's tools appear in the Message section. Click a tool to see and enter any required arguments.

5. Click Run to send the request to the MCP server. The response appears in the Response section.