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tables_db_decrement_row_column

Decrease a numeric value in a specific database table cell by a defined amount, useful for updating counters, inventory quantities, or scores.

Instructions

Decrement a specific column of a row by a given value.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
database_idYesDatabase ID.
table_idYesTable ID.
row_idYesRow ID.
columnYesColumn key.
valueNoValue to increment the column by. The value must be a number.
minNoMinimum value for the column. If the current value is lesser than this value, an exception will be thrown.
transaction_idNoTransaction ID for staging the operation.

Implementation Reference

  • MCP server tool handler that executes the tool 'tables_db_decrement_row_column' by calling the bound method from the TablesDB service.
    @server.call_tool()
    async def handle_call_tool(
        name: str, arguments: dict | None
    ) -> list[types.TextContent | types.ImageContent | types.EmbeddedResource]:
        
        try:
            tool_info = tools_manager.get_tool(name)
            if not tool_info:
                raise McpError(f"Tool {name} not found")
            
            bound_method = tool_info["function"]
            result = bound_method(**(arguments or {}))
            if hasattr(result, 'to_dict'):
                result_dict = result.to_dict()
                return [types.TextContent(type="text", text=str(result_dict))]
            return [types.TextContent(type="text", text=str(result))]
        except AppwriteException as e:
            return [types.TextContent(type="text", text=f"Appwrite Error: {str(e)}")]
        except Exception as e:
            return [types.TextContent(type="text", text=f"Error: {str(e)}")]
  • Registers the 'tables_db' service wrapping Appwrite TablesDB(client), which exposes its methods as MCP tools prefixed with 'tables_db_', including 'tables_db_decrement_row_column'.
    def register_services(args):
        # If --all is specified, enable all services
        if args.all:
            args.tables_db = args.users = args.teams = args.storage = True
            args.functions = args.messaging = args.locale = args.avatars = True
            args.sites = True
    
        # Register services based on CLI arguments
        if args.tables_db:
            tools_manager.register_service(Service(TablesDB(client), "tables_db"))
        if args.users:
            tools_manager.register_service(Service(Users(client), "users"))
        if args.teams:
            tools_manager.register_service(Service(Teams(client), "teams"))
        if args.storage:
            tools_manager.register_service(Service(Storage(client), "storage"))
        if args.functions:
            tools_manager.register_service(Service(Functions(client), "functions"))
        if args.messaging:
            tools_manager.register_service(Service(Messaging(client), "messaging"))
        if args.locale:
            tools_manager.register_service(Service(Locale(client), "locale"))
        if args.avatars:
            tools_manager.register_service(Service(Avatars(client), "avatars"))
        if args.sites:
            tools_manager.register_service(Service(Sites(client), "sites"))
        if args.databases:
            tools_manager.register_service(Service(Databases(client), "databases"))
    
        # If no services were specified, enable tables_db by default
        if not any([args.databases, args.tables_db, args.users, args.teams, args.storage,
                    args.functions, args.messaging, args.locale, args.avatars, args.sites]):
            tools_manager.register_service(Service(TablesDB(client), "tables_db"))
  • Dynamically generates tool definitions and input schemas for all public methods of the TablesDB service, constructing names like 'tables_db_decrement_row_column' and parsing parameters from signatures and docstrings.
    def list_tools(self) -> Dict[str, Dict]:
        """Lists all available tools for this service"""
        tools = {}
    
        for name, func in inspect.getmembers(self.service, predicate=inspect.ismethod):
            if name.startswith('_'): # Skip private methods
                continue
    
            original_func = func.__func__
            
            # Skip if not from the service's module
            if original_func.__module__ != self.service.__class__.__module__:
                continue
    
            # Get the overridden name if it exists
            tool_name = self._method_name_overrides.get(name, f"{self.service_name}_{name}")
    
            docstring = parse(original_func.__doc__)
            signature = inspect.signature(original_func)
            type_hints = get_type_hints(original_func)
    
            properties = {}
            required = []
    
            for param_name, param in signature.parameters.items():
                if param_name == 'self':
                    continue
    
                param_type = type_hints.get(param_name, str)
                properties[param_name] = self.python_type_to_json_schema(param_type)
                properties[param_name]["description"] = f"Parameter '{param_name}'"
                
                for doc_param in docstring.params:
                    if doc_param.arg_name == param_name:
                        properties[param_name]["description"] = doc_param.description
    
                if param.default is param.empty:
                    required.append(param_name)
    
            tool_definition = Tool(
                name=tool_name,
                description=f"{docstring.short_description or "No description available"}",
                inputSchema={
                    "type": "object",
                    "properties": properties,
                    "required": required
                }
            )
            
            tools[tool_name] = {
                "definition": tool_definition,
                "function": func
            }
            
        return tools
  • Helper function that converts Python type annotations to JSON Schema for tool input parameters.
    def python_type_to_json_schema(self, py_type: Any) -> dict:
        """Converts Python type hints to JSON Schema types."""
        type_mapping = {
            str: "string",
            int: "integer",
            float: "number",
            bool: "boolean",
            list: "array",
            dict: "object"
        }
        
        # Handle basic types
        if py_type in type_mapping:
            return {"type": type_mapping[py_type]}
        
        # Handle Optional types (Union[type, None])
        if hasattr(py_type, "__origin__") and py_type.__origin__ is Union:
            args = getattr(py_type, "__args__", ())
            if len(args) == 2 and args[1] is type(None):
                schema = self.python_type_to_json_schema(args[0])
                return schema
        
        # Handle List, Dict, and other generic types
        if hasattr(py_type, "__origin__"):
            origin = py_type.__origin__
            args = getattr(py_type, "__args__", ())
            
            # Handle List[T]
            if origin is list or origin is List:
                if args:
                    item_schema = self.python_type_to_json_schema(args[0])
                    return {
                        "type": "array",
                        "items": item_schema
                    }
                return {"type": "array"}
            
            # Handle Dict[K, V]
            if origin is dict or origin is Dict:
                if len(args) >= 2:
                    value_schema = self.python_type_to_json_schema(args[1])
                    return {
                        "type": "object",
                        "additionalProperties": value_schema
                    }
                return {"type": "object"}
        
        # Default to string for unknown types
        return {"type": "string"}
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions the decrement operation but fails to describe what happens on success/failure, whether it's atomic, if it requires specific permissions, or what errors might occur. The description is too minimal for a mutation tool with 7 parameters.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence that states exactly what the tool does without any wasted words. It's appropriately sized for a straightforward operation and front-loads the core functionality.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with 7 parameters, no annotations, and no output schema, the description is insufficient. It doesn't explain what happens when the operation succeeds, what gets returned, or important behavioral aspects like the 'min' parameter's exception behavior mentioned in the schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema description coverage is 100%, so all parameters are documented in the schema itself. The description adds no additional parameter information beyond what's already in the schema, meeting the baseline expectation but not providing extra value.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb ('decrement') and resource ('a specific column of a row'), making the purpose immediately understandable. However, it doesn't distinguish this tool from its sibling 'tables_db_increment_row_column' beyond the direction of the operation, which is why it doesn't reach a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives like 'tables_db_update_row' or 'tables_db_increment_row_column'. There's no mention of prerequisites, constraints, or typical use cases, leaving the agent with minimal context for selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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