describe_db_instance_performance

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

The description aligns with the readOnlyHint annotation by stating 'Queries' and 'provides performance data'. It adds minimal behavioral context beyond the annotation, such as the source (RDS OpenAPI) and a list of example metrics, but omits details like error handling or result format.

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

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

The description is concise, using a short paragraph followed by a structured Args list. Each sentence earns its place, though the Args section could be slightly more organized (e.g., bullet points). No superfluous information.

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

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

The tool has 6 required parameters and no output schema. The description covers what the tool does and parameter examples, but it does not describe the return format, response structure, or any constraints (e.g., time zone for dates). This leaves some gaps for an agent to fully understand the tool's behavior.

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

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

With 0% schema description coverage, the description provides brief explanations for all 6 parameters and example values (e.g., region_id: 'cn-hangzhou', perf_keys: array examples). This adds meaning beyond the bare schema, but the explanations are terse and could be more precise (e.g., date format for start_time).

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

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

The description clearly states that the tool queries performance data of an RDS instance and lists example metrics (MemCpuUsage, QPSTPS, etc.). It distinguishes this tool from sibling describe_* tools by specifying performance data, making its purpose unique.

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

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 describe_db_instance_parameters or describe_monitor_metrics. It does not discuss prerequisites, limitations, or scenarios where this tool is appropriate.

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