feat(mcp): implement caching for MCP tools to optimize loading

feat(onboard): enhance API key validation logic to retain existing keys
test(mcp): add tests for MCP tool caching behavior

tests/test_agent_mcp_cache.py

@@ -0,0 +1,59 @@
+"""Tests for MCP tool caching in EvoScientist.EvoScientist."""
+
+from __future__ import annotations
+
+import EvoScientist.EvoScientist as agent_module
+
+
+def _reset_mcp_cache() -> None:
+    agent_module._MCP_TOOLS_CACHE_KEY = None
+    agent_module._MCP_TOOLS_CACHE_VALUE = None
+
+
+class TestMcpToolCaching:
+    def setup_method(self) -> None:
+        _reset_mcp_cache()
+
+    def test_reuses_cached_tools_when_config_unchanged(self, monkeypatch):
+        calls = {"load": 0}
+        tool = object()
+
+        monkeypatch.setattr(
+            "EvoScientist.mcp.client.load_mcp_config",
+            lambda: {"srv": {"transport": "stdio", "command": "demo"}},
+        )
+
+        def fake_load_mcp_tools():
+            calls["load"] += 1
+            return {"main": [tool]}
+
+        monkeypatch.setattr(agent_module, "load_mcp_tools", fake_load_mcp_tools)
+
+        first = agent_module._load_mcp_tools_cached()
+        second = agent_module._load_mcp_tools_cached()
+
+        assert calls["load"] == 1
+        assert first == second
+        assert first is not second
+        assert first["main"] is not second["main"]
+
+    def test_reload_when_config_changes(self, monkeypatch):
+        calls = {"load": 0}
+        state = {"cfg": {"srv": {"transport": "stdio", "command": "v1"}}}
+
+        def fake_load_config():
+            return state["cfg"]
+
+        def fake_load_mcp_tools():
+            calls["load"] += 1
+            return {"main": [f"tool-v{calls['load']}"]}
+
+        monkeypatch.setattr("EvoScientist.mcp.client.load_mcp_config", fake_load_config)
+        monkeypatch.setattr(agent_module, "load_mcp_tools", fake_load_mcp_tools)
+
+        first = agent_module._load_mcp_tools_cached()
+        state["cfg"] = {"srv": {"transport": "stdio", "command": "v2"}}
+        second = agent_module._load_mcp_tools_cached()
+
+        assert calls["load"] == 2
+        assert first != second