dart_mcp (Package of the Week)

The Dart MCP package provides a framework for building model context protocol servers and clients, otherwise known as MCP. It's a standard for connecting AI models to resources, tools, and customize workflows. For example, it powers the Dart and Flutter MCP server. Resources provide access to local files, structured data, and any additional context that augments the model. — Tools enable models to execute some action or retrieve some information. And prompts guide users to follow a predefined path with each interaction. MCP servers act as universal adapters for exposing these resources, tools, and prompts. And MCP clients act as universal adapters for consuming these resources, tools, and prompts. Let's build an MCP server with a tool that helps me to convert between imperial and metric units. Each of the server features are provided as Dart mixins. Define a new tool by providing a name, description, and input schema. Next, declare a function that accepts a call tool request and returns a future or call tool result. Call tool request has an arguments property, which contains the data needed to fulfill the request. It matches the properties list in the input schema. After the calculations are done, the function should return a call tool result with a list of content objects containing the result. Content objects can be text, images, audio, or an embedded resource. Finally, remember to register the tool to link the tool definition to the tool implementation. Let's start the MCP server on a separate process using dart run. Next, using the MCP client constructor, create an MCP client and connect it to the MCP server. In this example, let's assume the server and client are running on the same machine. So, we're using the console's input output channel. However, if the MCP server and client were on separate machines, they could still communicate using a stream channel. A long-lived two-way communications pipe between a server and client. Before we can query it, initialize a handshake with the MCP server to declare what protocol to use and to discover what tools, resources, and prompt features are provided by the server. To initiate a tool request, construct a call tool request and provide the tool name and a map of arguments. Then use the server's call tool method and provide your call tool request. For more information on Dart MCP and all the other packages, head to pub. dev. —