Restore constructor backward compatibility for instructions

Author: 0xeb

examples/server_metadata.cpp

@@ -47,8 +47,9 @@ int main()
 
     std::cout << "2. Creating server with full metadata...\n";
 
-    // Server constructor signature (v2.13.0+):
-    //   Server(name, version, website_url, icons, strict_input_validation)
+    // Server constructor signatures:
+    //   Preferred: Server(name, version, website_url, icons, instructions, strict_input_validation)
+    //   Legacy-compatible: Server(name, version, website_url, icons, strict_input_validation)
     auto server = std::make_shared<server::Server>("example_server",      // name (required)
                                                    "1.2.3",               // version (required)
                                                    "https://example.com", // website_url (optional)

include/fastmcpp/app.hpp

@@ -8,6 +8,7 @@
 #include "fastmcpp/tools/manager.hpp"
 
 #include <chrono>
+#include <initializer_list>
 #include <memory>
 #include <optional>
 #include <string>
@@ -117,6 +118,16 @@ class FastMCP
                      std::optional<std::string> instructions = std::nullopt,
                      std::vector<std::shared_ptr<providers::Provider>> providers = {},
                      int list_page_size = 0, bool dereference_schemas = true);
+    /// Backward-compatible constructor overload (legacy parameter order).
+    FastMCP(std::string name, std::string version, std::optional<std::string> website_url,
+            std::optional<std::vector<Icon>> icons,
+            std::vector<std::shared_ptr<providers::Provider>> providers,
+            int list_page_size = 0, bool dereference_schemas = true);
+    /// Backward-compatible constructor overload for `{}` provider arguments.
+    FastMCP(std::string name, std::string version, std::optional<std::string> website_url,
+            std::optional<std::vector<Icon>> icons,
+            std::initializer_list<std::shared_ptr<providers::Provider>> providers,
+            int list_page_size = 0, bool dereference_schemas = true);
 
     // Metadata accessors
     const std::string& name() const

include/fastmcpp/server/server.hpp

@@ -18,6 +18,7 @@ namespace fastmcpp::server
 /// - version: Server version (optional)
 /// - website_url: Optional URL to server website
 /// - icons: Optional list of icons for UI display
+/// - instructions: Optional instructions shown during initialize
 /// - strict_input_validation: Flag for input validation behavior (optional)
 class Server
 {
@@ -36,6 +37,13 @@ class Server
           strict_input_validation_(std::move(strict_input_validation))
     {
     }
+    /// Backward-compatible constructor overload (legacy parameter order).
+    Server(std::string name, std::string version, std::optional<std::string> website_url,
+           std::optional<std::vector<fastmcpp::Icon>> icons, bool strict_input_validation)
+        : Server(std::move(name), std::move(version), std::move(website_url), std::move(icons),
+                 std::nullopt, strict_input_validation)
+    {
+    }
 
     // Route registration
     void route(const std::string& name, Handler h)

src/app.cpp

@@ -32,6 +32,25 @@ FastMCP::FastMCP(std::string name, std::string version, std::optional<std::strin
             throw ValidationError("provider cannot be null");
 }
 
+FastMCP::FastMCP(std::string name, std::string version, std::optional<std::string> website_url,
+                 std::optional<std::vector<Icon>> icons,
+                 std::vector<std::shared_ptr<providers::Provider>> providers, int list_page_size,
+                 bool dereference_schemas)
+    : FastMCP(std::move(name), std::move(version), std::move(website_url), std::move(icons),
+              std::nullopt, std::move(providers), list_page_size, dereference_schemas)
+{
+}
+
+FastMCP::FastMCP(std::string name, std::string version, std::optional<std::string> website_url,
+                 std::optional<std::vector<Icon>> icons,
+                 std::initializer_list<std::shared_ptr<providers::Provider>> providers,
+                 int list_page_size, bool dereference_schemas)
+    : FastMCP(std::move(name), std::move(version), std::move(website_url), std::move(icons),
+              std::nullopt, std::vector<std::shared_ptr<providers::Provider>>(providers),
+              list_page_size, dereference_schemas)
+{
+}
+
 namespace
 {
 fastmcpp::Json schema_from_schema_or_simple(const fastmcpp::Json& schema_or_simple)

tests/mcp/test_instructions.cpp

@@ -256,6 +256,34 @@ static void test_server_accessors()
     std::cout << "  PASS\n";
 }
 
+// ============================================================================
+// 11. Backward-compatible constructor parameter order
+// ============================================================================
+static void test_legacy_constructor_compatibility()
+{
+    std::cout << "test_legacy_constructor_compatibility...\n";
+
+    std::vector<std::shared_ptr<providers::Provider>> providers;
+    FastMCP app_with_vector("legacy_app_vector", "1.0.0", std::nullopt, std::nullopt, providers, 3,
+                            false);
+    assert(!app_with_vector.instructions().has_value());
+    assert(app_with_vector.list_page_size() == 3);
+    assert(!app_with_vector.dereference_schemas());
+
+    FastMCP app_with_braces("legacy_app_braces", "1.0.0", std::nullopt, std::nullopt, {}, 0,
+                            false);
+    assert(!app_with_braces.instructions().has_value());
+    assert(app_with_braces.list_page_size() == 0);
+    assert(!app_with_braces.dereference_schemas());
+
+    server::Server legacy_srv("legacy_srv", "1.0.0", std::nullopt, std::nullopt, true);
+    assert(!legacy_srv.instructions().has_value());
+    assert(legacy_srv.strict_input_validation().has_value());
+    assert(*legacy_srv.strict_input_validation());
+
+    std::cout << "  PASS\n";
+}
+
 int main()
 {
     test_bare_handler_with_instructions();
@@ -268,6 +296,7 @@ int main()
     test_proxy_instructions();
     test_proxy_set_instructions();
     test_server_accessors();
+    test_legacy_constructor_compatibility();
 
     std::cout << "All instructions tests passed\n";
     return 0;