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Alibaba Cloud MCP Server

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by aliyun

ReplaceSystemDisk

Replace the system disk of Alibaba Cloud ECS instances to update or change the operating system, using specified image files across multiple instances.

Instructions

批量替换ECS实例的系统盘,更换操作系统

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
ImageIdYes镜像ID
InstanceIdsYesAlibabaCloud ECS instance ID List
RegionIdNoAlibabaCloud region IDcn-hangzhou

Implementation Reference

  • Handler function OOS_ReplaceSystemDisk that batches replaces the system disk of multiple ECS instances using Alibaba Cloud OOS template 'ACS-ECS-BulkyReplaceSystemDisk'.
    @tools.append
    def OOS_ReplaceSystemDisk(
        InstanceIds: List[str] = Field(description='AlibabaCloud ECS instance ID List'),
        ImageId: str = Field(description='Image ID'),
        RegionId: str = Field(description='AlibabaCloud region ID', default='cn-hangzhou')
    ):
        """批量替换ECS实例的系统盘,更换操作系统"""
        parameters = {
            'regionId': RegionId,
            'resourceType': 'ALIYUN::ECS::Instance',
            'targets': {
                'ResourceIds': InstanceIds,
                'RegionId': RegionId,
                'Type': 'ResourceIds'
            },
            'imageId': ImageId
        }
        return _start_execution_sync(region_id=RegionId, template_name='ACS-ECS-BulkyReplaceSystemDisk', parameters=parameters)
  • Registration of all OOS tools (including OOS_ReplaceSystemDisk) to the FastMCP server instance.
    for tool in oos_tools.tools:
        mcp.tool(tool)
  • Shared helper function used by OOS tools to start an OOS execution and wait synchronously for its completion.
    def _start_execution_sync(region_id: str, template_name: str, parameters: dict):
        client = create_client(region_id=region_id)
        start_execution_request = oos_20190601_models.StartExecutionRequest(
            region_id=region_id,
            template_name=template_name,
            parameters=json.dumps(parameters)
        )
        start_execution_resp = client.start_execution(start_execution_request)
        execution_id = start_execution_resp.body.execution.execution_id
    
        while True:
            list_executions_request = oos_20190601_models.ListExecutionsRequest(
                region_id=region_id,
                execution_id=execution_id
            )
            list_executions_resp = client.list_executions(list_executions_request)
            status = list_executions_resp.body.executions[0].status
            if status == FAILED:
                status_message = list_executions_resp.body.executions[0].status_message
                raise exception.OOSExecutionFailed(reason=status_message)
            elif status in END_STATUSES:
                return list_executions_resp.body
            time.sleep(1)
Behavior2/5

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

No annotations are provided, so the description carries full burden. It states this is a batch operation and changes the OS, implying it's destructive and may require downtime, but doesn't disclose critical behavioral traits: whether instances must be stopped first, if data on the system disk is lost, authentication requirements, rate limits, or expected response format. The description adds minimal value beyond the basic action.

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 in Chinese that front-loads the core action ('批量替换ECS实例的系统盘') and adds clarifying outcome ('更换操作系统'). There is zero wasted text, making it appropriately concise for a tool with clear parameters in the schema.

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?

Given this is a complex, destructive operation with no annotations and no output schema, the description is insufficient. It lacks details on behavioral implications (e.g., downtime, data loss), prerequisites, error handling, or return values. For a batch mutation tool affecting system disks, more context is needed to ensure safe and correct usage.

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?

Schema description coverage is 100%, so the schema already documents all parameters (ImageId, InstanceIds, RegionId). The description adds no additional meaning about parameters beyond implying ImageId relates to the new OS and InstanceIds are for batch processing. Baseline 3 is appropriate when schema does the heavy lifting.

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 action ('批量替换' meaning 'batch replace') and resource ('ECS实例的系统盘' meaning 'ECS instance system disk'), with the additional context '更换操作系统' (change operating system) that clarifies the outcome. However, it doesn't explicitly differentiate from sibling tools like 'RebootInstances' or 'StopInstances' which also affect instances but in different ways.

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. It doesn't mention prerequisites (e.g., instances must be stopped), exclusions (e.g., cannot replace disks for running instances), or compare to siblings like 'RunInstances' (for creating new instances) or 'DescribeImages' (for selecting images).

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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