The Model Context Protocol allows clients to get notified when a resource has changed.
This allows clients to do things like refresh the LLMs context when an underlying resource has changed.
Lets say you have some application logs in a resource, the server could periodically refresh the application log resource to allow the client to get latest logs.
Implementation
In mcp-golang, the server will send a notification to the client when any of the following events occur:
- A new tool is registered via the
RegisterTool
function
- A new prompt is registered via the
RegisterPrompt
function
- A new resource is registered via the
RegisterResource
function
- A prompt is deregistered via the
DeregisterPrompt
function
- A tool is deregistered via the
DeregisterTool
function
- A resource is deregistered via the
DeregisterResource
function
A silly e2e example of this is the server below. It registers and deregisters a tool, prompt, and resource every second causing 3 notifications to be sent to the client each second.
package main
import (
"fmt"
mcp_golang "github.com/metoro-io/mcp-golang"
"github.com/metoro-io/mcp-golang/transport/stdio"
"time"
)
type HelloArguments struct {
Submitter string `json:"submitter" jsonschema:"required,description=The name of the thing calling this tool (openai or google or claude etc)'"`
}
type Content struct {
Title string `json:"title" jsonschema:"required,description=The title to submit"`
Description *string `json:"description" jsonschema:"description=The description to submit"`
}
func main() {
done := make(chan struct{})
server := mcp_golang.NewServer(stdio.NewStdioServerTransport())
err := server.Serve()
if err != nil {
panic(err)
}
go func() {
for {
err := server.RegisterTool("hello", "Say hello to a person", func(arguments HelloArguments) (*mcp_golang.ToolResponse, error) {
return mcp_golang.NewToolResponse(mcp_golang.NewTextContent(fmt.Sprintf("Hello, %s!", arguments.Submitter))), nil
})
if err != nil {
panic(err)
}
time.Sleep(1 * time.Second)
err = server.DeregisterTool("hello")
if err != nil {
panic(err)
}
}
}()
go func() {
for {
err = server.RegisterPrompt("prompt_test", "This is a test prompt", func(arguments Content) (*mcp_golang.PromptResponse, error) {
return mcp_golang.NewPromptResponse("description", mcp_golang.NewPromptMessage(mcp_golang.NewTextContent(fmt.Sprintf("Hello, %server!", arguments.Title)), mcp_golang.RoleUser)), nil
})
if err != nil {
panic(err)
}
time.Sleep(1 * time.Second)
err = server.DeregisterPrompt("prompt_test")
if err != nil {
panic(err)
}
}
}()
go func() {
err = server.RegisterResource("test://resource", "resource_test", "This is a test resource", "application/json", func() (*mcp_golang.ResourceResponse, error) {
return mcp_golang.NewResourceResponse(mcp_golang.NewTextEmbeddedResource("test://resource", "This is a test resource", "application/json")), nil
})
if err != nil {
panic(err)
}
time.Sleep(1 * time.Second)
err = server.DeregisterResource("test://resource")
if err != nil {
panic(err)
}
}()
<-done
}