feat: Implement clean variables object for remote URL templating

Replace array-based variables with an object where keys are variable names
and values are Input definitions. This provides a much cleaner API and
enables rich client UIs.

Key improvements:
- Variables as object: {"tenant_id": {"description": "...", "isRequired": true}}
- No duplicate 'name' field - variable name is the object key
- Full Input capabilities: choices, isSecret, default, format, etc.
- Consistent with existing InputWithVariables pattern
- Client-friendly for building rich UIs (dropdowns, validation, etc.)

Example:
{
  "url": "https://api.example.github.io/mcp/{tenant_id}",
  "variables": {
    "tenant_id": {
      "description": "Tenant identifier",
      "isRequired": true,
      "choices": ["us-cell1", "emea-cell1"]
    }
  }
}

All validation and tests pass. Schema, Go types, validators, and example
have been updated to support the new structure.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: tadasant

docs/reference/server-json/generic-server-json.md

@@ -683,13 +683,12 @@ This example demonstrates URL templating for remote servers, useful for multi-te
     {
       "type": "streamable-http",
       "url": "https://api.example.github.io/mcp/{tenant_id}",
-      "variables": [
-        {
-          "name": "tenant_id",
+      "variables": {
+        "tenant_id": {
           "description": "Tenant identifier (e.g., 'us-cell1', 'emea-cell1')",
           "isRequired": true
         }
-      ]
+      }
     }
   ]
 }

docs/reference/server-json/server.schema.json

@@ -377,7 +377,7 @@
         },
         "url": {
           "type": "string",
-          "description": "URL template for the streamable-http transport. Variables in {curly_braces} reference variable names from the 'variables' array. If variables are not provided, {curly_braces} should be treated as literal text. After variable substitution, this should produce a valid URI.",
+          "description": "URL template for the streamable-http transport. Variables in {curly_braces} reference variable names from the 'variables' object. If variables are not provided, {curly_braces} should be treated as literal text. After variable substitution, this should produce a valid URI.",
           "example": "https://api.example.com/mcp"
         },
         "headers": {
@@ -388,10 +388,10 @@
           }
         },
         "variables": {
-          "type": "array",
-          "description": "Configuration variables that can be referenced in URL template {curly_braces} via their name property",
-          "items": {
-            "$ref": "#/definitions/KeyValueInput"
+          "type": "object",
+          "description": "Configuration variables that can be referenced in URL template {curly_braces}. The key is the variable name, and the value defines the variable properties.",
+          "additionalProperties": {
+            "$ref": "#/definitions/Input"
           }
         }
       }
@@ -414,7 +414,7 @@
         "url": {
           "type": "string",
           "format": "uri",
-          "description": "Server-Sent Events endpoint URL template. Variables in {curly_braces} reference variable names from the 'variables' array. If variables are not provided, {curly_braces} should be treated as literal text. After variable substitution, this should produce a valid URI.",
+          "description": "Server-Sent Events endpoint URL template. Variables in {curly_braces} reference variable names from the 'variables' object. If variables are not provided, {curly_braces} should be treated as literal text. After variable substitution, this should produce a valid URI.",
           "example": "https://mcp-fs.example.com/sse"
         },
         "headers": {
@@ -425,10 +425,10 @@
           }
         },
         "variables": {
-          "type": "array",
-          "description": "Configuration variables that can be referenced in URL template {curly_braces} via their name property",
-          "items": {
-            "$ref": "#/definitions/KeyValueInput"
+          "type": "object",
+          "description": "Configuration variables that can be referenced in URL template {curly_braces}. The key is the variable name, and the value defines the variable properties.",
+          "additionalProperties": {
+            "$ref": "#/definitions/Input"
           }
         }
       }

internal/validators/validators.go

@@ -296,10 +296,10 @@ func collectAvailableVariables(pkg *model.Package) []string {
 func collectRemoteTransportVariables(transport *model.Transport) []string {
 	var variables []string
 
-	// Add variable names from the Variables field
-	for _, variable := range transport.Variables {
-		if variable.Name != "" {
-			variables = append(variables, variable.Name)
+	// Add variable names from the Variables map
+	for variableName := range transport.Variables {
+		if variableName != "" {
+			variables = append(variables, variableName)
 		}
 	}
 

pkg/model/types.go

@@ -11,10 +11,10 @@ const (
 
 // Transport represents transport configuration with optional URL templating
 type Transport struct {
-	Type      string          `json:"type"`
-	URL       string          `json:"url,omitempty"`
-	Headers   []KeyValueInput `json:"headers,omitempty"`
-	Variables []KeyValueInput `json:"variables,omitempty"`
+	Type      string           `json:"type"`
+	URL       string           `json:"url,omitempty"`
+	Headers   []KeyValueInput  `json:"headers,omitempty"`
+	Variables map[string]Input `json:"variables,omitempty"`
 }
 
 // Package represents a package configuration