Feat: Scratch MCP tool calling support. (#8263)

### What problem does this PR solve?

This is a cherry-pick from #7781 as requested.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

api/db/__init__.py

@@ -104,4 +104,9 @@ class CanvasType(StrEnum):
     ChatBot = "chatbot"
     DocBot = "docbot"
 
+
+class MCPServerType(StrEnum):
+    SSE = "sse"
+    StreamableHttp = "streamable-http"
+
 KNOWLEDGEBASE_FOLDER_NAME=".knowledgebase"

api/db/db_models.py

@@ -799,6 +799,20 @@ class UserCanvasVersion(DataBaseModel):
         db_table = "user_canvas_version"
 
 
+class MCPServer(DataBaseModel):
+    id = CharField(max_length=32, primary_key=True)
+    name = CharField(max_length=255, null=False, help_text="MCP Server name")
+    tenant_id = CharField(max_length=32, null=False, index=True)
+    url = CharField(max_length=2048, null=False, help_text="MCP Server URL")
+    server_type = CharField(max_length=32, null=False, help_text="MCP Server type")
+    description = TextField(null=True, help_text="MCP Server description")
+    variables = JSONField(null=True, default=[], help_text="MCP Server variables")
+    headers = JSONField(null=True, default={}, help_text="MCP Server additional request headers")
+
+    class Meta:
+        db_table = "mcp_server"
+
+ 
 class Search(DataBaseModel):
     id = CharField(max_length=32, primary_key=True)
     avatar = TextField(null=True, help_text="avatar base64 string")
@@ -934,3 +948,7 @@ def migrate_db():
         migrate(migrator.add_column("llm", "is_tools", BooleanField(null=False, help_text="support tools", default=False)))
     except Exception:
         pass
+    try:
+        migrate(migrator.add_column("mcp_server", "variables", JSONField(null=True, help_text="MCP Server variables", default=[])))
+    except Exception:
+        pass

api/db/services/mcp_server_service.py

@@ -0,0 +1,61 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+from api.db.db_models import DB, MCPServer
+from api.db.services.common_service import CommonService
+
+
+class MCPServerService(CommonService):
+    """Service class for managing MCP server related database operations.
+
+    This class extends CommonService to provide specialized functionality for MCP server management,
+    including MCP server creation, updates, and deletions.
+
+    Attributes:
+        model: The MCPServer model class for database operations.
+    """
+
+    model = MCPServer
+
+    @classmethod
+    @DB.connection_context()
+    def get_servers(cls, tenant_id: str, id_list: list[str] | None = None):
+        """Retrieve all MCP servers associated with a tenant.
+
+        This method fetches all MCP servers for a given tenant, ordered by creation time.
+        It only includes fields for list display.
+
+        Args:
+            tenant_id (str): The unique identifier of the tenant.
+            id_list (list[str]): Get servers by ID list. Will ignore this condition if None.
+
+        Returns:
+            list[dict]: List of MCP server dictionaries containing MCP server details.
+                       Returns None if no MCP servers are found.
+        """
+        fields = [
+            cls.model.id, cls.model.name, cls.model.server_type, cls.model.url, cls.model.description, 
+            cls.model.variables, cls.model.update_date
+        ]
+
+        servers = cls.model.select(*fields).order_by(cls.model.create_time.desc()).where(cls.model.tenant_id == tenant_id)
+
+        if id_list is not None:
+            servers = servers.where(cls.model.id.in_(id_list))
+
+        servers = list(servers.dicts())
+        if not servers:
+            return None
+        return servers