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Alibaba Cloud RDS OpenAPI MCP Server

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by aliyun
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Python
Remote

describe_db_instances

Read-only

Retrieve details of Alibaba Cloud RDS database instances in a specified region to manage and monitor your cloud database resources.

Instructions

Queries instances.
Args:
    region_id: queries instances in region id(e.g. cn-hangzhou)
:return:

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
region_idYes

Implementation Reference

  • src/alibabacloud_rds_openapi_mcp_server/server.py:67-89 (handler)
    The core handler function for the 'describe_db_instances' MCP tool. It creates a DescribeDBInstancesRequest, calls the RDS client's describe_dbinstances method via get_rds_client, processes the response into CSV format using json_array_to_csv, and returns the list of DB instances or a 'No RDS instances found.' message if empty.
    @mcp.tool(annotations=READ_ONLY_TOOL)
async def describe_db_instances(region_id: str):
    """
    Queries instances.
    Args:
        region_id: queries instances in region id(e.g. cn-hangzhou)
    :return:
    """
    client = get_rds_client(region_id)
    try:
        request = rds_20140815_models.DescribeDBInstancesRequest(
            region_id=region_id,
            page_size=100
        )
        response = client.describe_dbinstances(request)

        res = json_array_to_csv(response.body.items.dbinstance)
        if not res:
            return "No RDS instances found."
        return res
    except Exception as e:
        raise e

Tool Definition Quality

C2.4/5.0
Behavior3/5

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

The annotations provide readOnlyHint=true, indicating this is a safe read operation. The description adds minimal behavioral context by specifying it queries instances in a region, but doesn't disclose details like pagination, rate limits, or what the return format looks like. Since annotations cover the safety aspect, the description adds some value but lacks depth, making it adequate but with clear gaps.

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

Conciseness4/5

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

The description is brief and front-loaded with the main action ('Queries instances'), followed by parameter details. It avoids unnecessary words, but the structure could be improved by clarifying the tool's purpose more explicitly upfront. Overall, it's efficient but slightly under-specified.

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 the tool has one required parameter, no output schema, and annotations only cover read-only status, the description is incomplete. It doesn't explain what 'instances' are, what data is returned, or how to interpret results. For a query tool with no output schema, more context is needed to make it useful for an AI agent.

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

Parameters2/5

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

The schema description coverage is 0%, so the description must compensate. It provides an example for region_id ('e.g. cn-hangzhou'), which adds some meaning beyond the schema's generic 'Region Id' title. However, it doesn't explain what region_id represents (e.g., a specific cloud region identifier) or any constraints, leaving the parameter only partially documented.

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

Purpose2/5

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

The description 'Queries instances' is a tautology that essentially restates the tool name 'describe_db_instances'. It doesn't specify what type of instances (database instances) or what information is returned. While the name suggests database instances, the description itself lacks the specificity needed to distinguish it from other query tools like 'describe_available_classes' or 'describe_vpcs'.

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?

There is no guidance on when to use this tool versus alternatives. The description doesn't mention what makes this tool unique compared to siblings like 'describe_db_instance_attribute' or 'describe_db_instance_performance'. No context is provided about prerequisites, such as needing a region_id, or when this tool is appropriate versus other describe_* tools.

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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