f · f · Mar 28, 2025 · Mar 28, 2025
diff --git a/README.md b/README.md
@@ -223,6 +223,100 @@ mcp mock prompt greeting "Greeting template" "Hello {{name}}! Welcome to {{locat
 
 When a client requests the prompt, it can provide values for these arguments which will be substituted in the response.
 
+## Proxy Mode
+
+The proxy mode allows you to register shell scripts as MCP tools and proxy MCP requests to them.
+The scripts will receive tool parameters as environment variables.
+
+### Registering a Tool
+
+To register a shell script as an MCP tool:
+
+```bash
+mcp proxy tool add_operation "Adds a and b" "a:int,b:int" ./examples/add.sh
+```
+
+This registers a tool named `add_operation` with the description "Adds a and b" and parameters `a` and `b` of type `int`.
+When the tool is called, the parameters will be passed as environment variables to the script.
+
+Parameters are specified in the format `name:type,name:type,...` where `type` can be `string`, `int`, `float`, or `bool`.
+
+### Starting the Proxy Server
+
+To start a proxy server with the registered tools:
+
+```bash
+mcp proxy start
+```
+
+The server will run in stdio mode compatible with the MCP protocol and forward tool call requests to the registered shell scripts.
+
+### Example Shell Scripts
+
+#### Adding Numbers
+
+```bash
+#!/bin/bash
+
+# Get the values from environment variables
+if [ -z "$a" ] || [ -z "$b" ]; then
+  echo "Error: Missing required parameters 'a' or 'b'"
+  exit 1
+fi
+
+# Try to convert to integers
+a_val=$(($a))
+b_val=$(($b))
+
+# Perform the addition
+result=$(($a_val + $b_val))
+
+# Return the result
+echo "The sum of $a and $b is $result"
+```
+
+#### Customized Greeting
+
+```bash
+#!/bin/bash
+
+# Get the values from environment variables
+if [ -z "$name" ]; then
+  echo "Error: Missing required parameter 'name'"
+  exit 1
+fi
+
+# Set default values if not provided
+if [ -z "$greeting" ]; then
+  greeting="Hello"
+fi
+
+if [ -z "$formal" ]; then
+  formal=false
+fi
+
+# Customize greeting based on formal flag
+if [ "$formal" = "true" ]; then
+  title="Mr./Ms."
+  message="${greeting}, ${title} ${name}. How may I assist you today?"
+else
+  message="${greeting}, ${name}! Nice to meet you!"
+fi
+
+# Return the greeting
+echo "$message"
+```
+
+Register with:
+
+```bash
+mcp proxy tool greet "Greets a user" "name:string,greeting:string,formal:bool" ./examples/greet.sh
+```
+
+### Configuration
+
+Tools are registered in `~/.mcpt/proxy_config.json`. The proxy server logs all requests and responses to `~/.mcpt/logs/proxy.log`.
+
 ## Examples
 
 List tools from a filesystem server:
@@ -252,6 +346,47 @@ mcp mock tool file_reader "Reads files" \
       resource docs://api "API Documentation" "# API Reference\n\nThis document describes the API."
 ```
 
+Using the proxy mode with a simple shell script:
+
+```bash
+# 1. Create a simple shell script for addition
+cat > add.sh << 'EOF'
+#!/bin/bash
+# Get values from environment variables
+if [ -z "$a" ] || [ -z "$b" ]; then
+  echo "Error: Missing required parameters 'a' or 'b'"
+  exit 1
+fi
+result=$(($a + $b))
+echo "The sum of $a and $b is $result"
+EOF
+
+# 2. Make it executable
+chmod +x add.sh
+
+# 3. Register it as an MCP tool
+mcp proxy tool add_numbers "Adds two numbers" "a:int,b:int" ./add.sh
+
+# 4. In one terminal, start the proxy server
+mcp proxy start
+
+# 5. In another terminal, you can call it as an MCP tool
+mcp call add_numbers --params '{"a":5,"b":3}' --format pretty
+```
+
+Tailing the logs to debug your proxy or mock server:
+
+```bash
+# For the mock server logs
+tail -f ~/.mcpt/logs/mock.log
+
+# For the proxy server logs
+tail -f ~/.mcpt/logs/proxy.log
+
+# To watch all logs in real-time (on macOS/Linux)
+find ~/.mcpt/logs -name "*.log" -exec tail -f {} \;
+```
+
 ## Contributing
 
 We welcome contributions! Please see our [Contributing Guidelines](CONTRIBUTING.md) 

diff --git a/cmd/mcptools/main.go b/cmd/mcptools/main.go
@@ -7,15 +7,18 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log"
 	"os"
 	"path/filepath"
 	"strings"
 
 	"github.com/f/mcptools/pkg/client"
 	"github.com/f/mcptools/pkg/jsonutils"
 	"github.com/f/mcptools/pkg/mock"
+	"github.com/f/mcptools/pkg/proxy"
 	"github.com/peterh/liner"
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 )
 
 // version information placeholders.
@@ -61,6 +64,7 @@ func main() {
 		newReadResourceCmd(),
 		newShellCmd(),
 		newMockCmd(),
+		proxyCmd(),
 	)
 
 	if err := rootCmd.Execute(); err != nil {
@@ -939,3 +943,137 @@ Example:
 
 	return cmd
 }
+
+func proxyCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "proxy",
+		Short: "Proxy MCP tool requests to shell scripts",
+		Long: `Proxy MCP tool requests to shell scripts.
+
+This command allows you to register shell scripts as MCP tools and proxy MCP requests to them.
+The scripts will receive tool parameters as environment variables.
+
+Examples:
+  # Register a shell script as an MCP tool
+  mcp proxy tool add_operation "Adds a and b" "a:int,b:int" ./add.sh
+
+  # Start a proxy server with the registered tools
+  mcp proxy start`,
+	}
+
+	cmd.AddCommand(proxyToolCmd())
+	cmd.AddCommand(proxyStartCmd())
+
+	return cmd
+}
+
+func proxyToolCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "tool NAME DESCRIPTION PARAMETERS SCRIPT_PATH",
+		Short: "Register a shell script as an MCP tool",
+		Long: `Register a shell script as an MCP tool.
+
+The PARAMETERS argument should be a comma-separated list of "name:type" pairs.
+Supported types: string, int, float, bool
+
+Example:
+  mcp proxy tool add_operation "Adds a and b" "a:int,b:int" ./add.sh`,
+		Args: cobra.ExactArgs(4),
+		Run: func(_ *cobra.Command, args []string) {
+			name := args[0]
+			description := args[1]
+			parameters := args[2]
+			scriptPath := args[3]
+
+			// Initialize config
+			viper.SetConfigName("proxy_config")
+			viper.SetConfigType("json")
+			viper.AddConfigPath("$HOME/.mcpt")
+
+			// Create config directory if it doesn't exist
+			configDir := os.ExpandEnv("$HOME/.mcpt")
+			if err := os.MkdirAll(configDir, 0o750); err != nil {
+				log.Fatalf("Error creating config directory: %v", err)
+			}
+
+			// Load existing config if it exists
+			var config map[string]map[string]string
+			var configFileNotFound viper.ConfigFileNotFoundError
+			err := viper.ReadInConfig()
+			if err != nil {
+				if errors.As(err, &configFileNotFound) {
+					// Config file not found, create a new one
+					config = make(map[string]map[string]string)
+				} else {
+					log.Fatalf("Error reading config: %v", err)
+				}
+			} else {
+				// Config file found, unmarshal it
+				config = make(map[string]map[string]string)
+				unmarshalErr := viper.Unmarshal(&config)
+				if unmarshalErr != nil {
+					log.Fatalf("Error unmarshaling config: %v", unmarshalErr)
+				}
+			}
+
+			// Add or update tool config
+			config[name] = map[string]string{
+				"description": description,
+				"parameters":  parameters,
+				"script":      scriptPath,
+			}
+
+			// Save config
+			configPath := os.ExpandEnv("$HOME/.mcpt/proxy_config.json")
+			configJSON, err := json.MarshalIndent(config, "", "  ")
+			if err != nil {
+				log.Fatalf("Error marshaling config: %v", err)
+			}
+
+			writeErr := os.WriteFile(configPath, configJSON, 0o600)
+			if writeErr != nil {
+				log.Fatalf("Error writing config: %v", writeErr)
+			}
+
+			fmt.Printf("Registered tool '%s' with script '%s'\n", name, scriptPath)
+		},
+	}
+
+	return cmd
+}
+
+func proxyStartCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "start",
+		Short: "Start a proxy server with registered tools",
+		Long: `Start a proxy server that forwards MCP tool requests to shell scripts.
+
+The server reads tool configurations from $HOME/.mcpt/proxy_config.json.
+
+Example:
+  mcp proxy start`,
+		Run: func(_ *cobra.Command, _ []string) {
+			// Load tool configurations
+			viper.SetConfigName("proxy_config")
+			viper.SetConfigType("json")
+			viper.AddConfigPath("$HOME/.mcpt")
+
+			if err := viper.ReadInConfig(); err != nil {
+				log.Fatalf("Error reading config: %v", err)
+			}
+
+			var config map[string]map[string]string
+			if err := viper.Unmarshal(&config); err != nil {
+				log.Fatalf("Error unmarshaling config: %v", err)
+			}
+
+			// Run proxy server
+			fmt.Println("Starting proxy server...")
+			if err := proxy.RunProxyServer(config); err != nil {
+				log.Fatalf("Error running proxy server: %v", err)
+			}
+		},
+	}
+
+	return cmd
+}
diff --git a/examples/add.sh b/examples/add.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Get the values from environment variables
+if [ -z "$a" ] || [ -z "$b" ]; then
+  echo "Error: Missing required parameters 'a' or 'b'"
+  exit 1
+fi
+
+# Try to convert to integers
+a_val=$(($a))
+b_val=$(($b))
+
+# Perform the addition
+result=$(($a_val + $b_val))
+
+# Return the result
+echo "The sum of $a and $b is $result" 
diff --git a/examples/greet.sh b/examples/greet.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Get the values from environment variables
+if [ -z "$name" ]; then
+  echo "Error: Missing required parameter 'name'"
+  exit 1
+fi
+
+# Set default values if not provided
+if [ -z "$greeting" ]; then
+  greeting="Hello"
+fi
+
+if [ -z "$formal" ]; then
+  formal=false
+fi
+
+# Customize greeting based on formal flag
+if [ "$formal" = "true" ]; then
+  title="Mr./Ms."
+  message="${greeting}, ${title} ${name}. How may I assist you today?"
+else
+  message="${greeting}, ${name}! Nice to meet you!"
+fi
+
+# Return the greeting
+echo "$message" 
diff --git a/go.mod b/go.mod
@@ -9,16 +9,28 @@ require (
 )
 
 require (
+	github.com/fsnotify/fsnotify v1.8.0 // indirect
+	github.com/go-viper/mapstructure/v2 v2.2.1 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/mattn/go-runewidth v0.0.16 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.3 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/sagikazarmark/locafero v0.7.0 // indirect
+	github.com/sourcegraph/conc v0.3.0 // indirect
+	github.com/spf13/afero v1.12.0 // indirect
+	github.com/spf13/cast v1.7.1 // indirect
 	github.com/spf13/pflag v1.0.6 // indirect
+	github.com/spf13/viper v1.20.1 // indirect
+	github.com/subosito/gotenv v1.6.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
 	golang.org/x/mod v0.17.0 // indirect
 	golang.org/x/sync v0.12.0 // indirect
 	golang.org/x/sys v0.31.0 // indirect
 	golang.org/x/term v0.30.0 // indirect
 	golang.org/x/text v0.23.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 	mvdan.cc/gofumpt v0.7.0 // indirect
 )