Fix the way we identify the URL registry type (#2576)

* Fix the way we identify the URL registry type

Signed-off-by: Radoslav Dimitrov <[email protected]>

* Add unit tests

Signed-off-by: Radoslav Dimitrov <[email protected]>

---------

Signed-off-by: Radoslav Dimitrov <[email protected]>

Author: rdimitrov

cmd/thv/app/config.go

@@ -161,7 +161,7 @@ func unsetCACertCmdFunc(_ *cobra.Command, _ []string) error {
 
 func setRegistryCmdFunc(_ *cobra.Command, args []string) error {
 	input := args[0]
-	registryType, cleanPath := config.DetectRegistryType(input)
+	registryType, cleanPath := config.DetectRegistryType(input, allowPrivateRegistryIp)
 
 	provider := config.NewDefaultProvider()
 

pkg/config/registry.go

@@ -1,7 +1,9 @@
 package config
 
 import (
+	"encoding/json"
 	"fmt"
+	"net/http"
 	neturl "net/url"
 	"path/filepath"
 	"strings"
@@ -19,7 +21,7 @@ const (
 )
 
 // DetectRegistryType determines if input is a URL or file path and returns cleaned path
-func DetectRegistryType(input string) (registryType string, cleanPath string) {
+func DetectRegistryType(input string, allowPrivateIPs bool) (registryType string, cleanPath string) {
 	// Check for explicit file:// protocol
 	if strings.HasPrefix(input, "file://") {
 		return RegistryTypeFile, strings.TrimPrefix(input, "file://")
@@ -28,17 +30,72 @@ func DetectRegistryType(input string) (registryType string, cleanPath string) {
 	// Check for HTTP/HTTPS URLs
 	if networking.IsURL(input) {
 		// If URL ends with .json, treat as static registry file
-		// Otherwise, treat as MCP Registry API endpoint
 		if strings.HasSuffix(input, ".json") {
 			return RegistryTypeURL, input
 		}
-		return RegistryTypeAPI, input
+
+		// For URLs without .json extension, probe to determine the type
+		registryType := probeRegistryURL(input, allowPrivateIPs)
+		return registryType, input
 	}
 
 	// Default: treat as file path
 	return RegistryTypeFile, filepath.Clean(input)
 }
 
+// probeRegistryURL attempts to determine if a URL is a static JSON file or an API endpoint
+// by checking if the URL returns valid ToolHive registry JSON or has an /openapi.yaml endpoint.
+func probeRegistryURL(url string, allowPrivateIPs bool) string {
+	// Create HTTP client for probing with user's private IP preference
+	client, err := networking.NewHttpClientBuilder().WithPrivateIPs(allowPrivateIPs).Build()
+	if err != nil {
+		// If we can't create a client, default to static JSON
+		return RegistryTypeURL
+	}
+
+	// First, try to fetch and parse as ToolHive registry JSON
+	if isValidRegistryJSON(client, url) {
+		return RegistryTypeURL
+	}
+
+	// If not valid JSON, check for /openapi.yaml endpoint (MCP Registry API)
+	openapiURL, err := neturl.JoinPath(url, "openapi.yaml")
+	if err == nil {
+		resp, err := client.Head(openapiURL)
+		if err == nil {
+			_ = resp.Body.Close()
+			// If openapi.yaml exists (200 OK), treat as API endpoint
+			if resp.StatusCode == http.StatusOK {
+				return RegistryTypeAPI
+			}
+		}
+	}
+
+	// Default to static JSON file (validation will catch errors later)
+	return RegistryTypeURL
+}
+
+// isValidRegistryJSON checks if a URL returns valid ToolHive registry JSON
+func isValidRegistryJSON(client *http.Client, url string) bool {
+	resp, err := client.Get(url)
+	if err != nil {
+		return false
+	}
+	defer resp.Body.Close()
+
+	// Try to parse as JSON with registry structure
+	// We just check for basic registry fields to avoid pulling in the full types package
+	var data map[string]interface{}
+	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
+		return false
+	}
+
+	// Check if it has registry-like structure (servers or remoteServers fields)
+	_, hasServers := data["servers"]
+	_, hasRemoteServers := data["remoteServers"]
+	return hasServers || hasRemoteServers
+}
+
 // setRegistryURL validates and sets a registry URL using the provided provider
 func setRegistryURL(provider Provider, registryURL string, allowPrivateRegistryIp bool) error {
 	// Validate URL scheme