diff --git a/claude_stderr.log b/claude_stderr.log
new file mode 100644
index 000000000..e69de29bb
diff --git a/docs/reference/api/openapi.yaml b/docs/reference/api/openapi.yaml
index e05c934d6..4a5ba691e 100644
--- a/docs/reference/api/openapi.yaml
+++ b/docs/reference/api/openapi.yaml
@@ -685,9 +685,9 @@ components:
           example: "streamable-http"
         url:
           type: string
-          description: "URL template for the streamable-http transport. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI."
+          description: "URL template for the streamable-http transport. Must start with http://, https://, or a template variable (e.g., {baseUrl}). Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI."
           example: "https://api.example.com/mcp"
-          pattern: "^https?://[^\\s]+$"
+          pattern: "^(https?://[^\\s]+|\\{[a-zA-Z_][a-zA-Z0-9_]*\\}[^\\s]*)$"
         headers:
           type: array
           description: HTTP headers to include
@@ -707,9 +707,9 @@ components:
           example: "sse"
         url:
           type: string
-          description: "Server-Sent Events endpoint URL template. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI."
+          description: "Server-Sent Events endpoint URL template. Must start with http://, https://, or a template variable (e.g., {baseUrl}). Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI."
           example: "https://mcp-fs.example.com/sse"
-          pattern: "^https?://[^\\s]+$"
+          pattern: "^(https?://[^\\s]+|\\{[a-zA-Z_][a-zA-Z0-9_]*\\}[^\\s]*)$"
         headers:
           type: array
           description: HTTP headers to include
diff --git a/docs/reference/server-json/server.schema.json b/docs/reference/server-json/server.schema.json
index e25191b19..04a5d1e43 100644
--- a/docs/reference/server-json/server.schema.json
+++ b/docs/reference/server-json/server.schema.json
@@ -511,9 +511,9 @@
           "type": "string"
         },
         "url": {
-          "description": "Server-Sent Events endpoint URL template. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.",
+          "description": "Server-Sent Events endpoint URL template. Must start with http://, https://, or a template variable (e.g., {baseUrl}). Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.",
           "example": "https://mcp-fs.example.com/sse",
-          "pattern": "^https?://[^\\s]+$",
+          "pattern": "^(https?://[^\\s]+|\\{[a-zA-Z_][a-zA-Z0-9_]*\\}[^\\s]*)$",
           "type": "string"
         }
       },
@@ -557,9 +557,9 @@
           "type": "string"
         },
         "url": {
-          "description": "URL template for the streamable-http transport. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.",
+          "description": "URL template for the streamable-http transport. Must start with http://, https://, or a template variable (e.g., {baseUrl}). Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.",
           "example": "https://api.example.com/mcp",
-          "pattern": "^https?://[^\\s]+$",
+          "pattern": "^(https?://[^\\s]+|\\{[a-zA-Z_][a-zA-Z0-9_]*\\}[^\\s]*)$",
           "type": "string"
         }
       },