get_device_last_data

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description does not need to restate safety. It adds a temporal scoping detail ('latest real-time') and lists return signal families, but with an output schema present this is complementary rather than substantial new behavioral disclosure. It also does not describe behavior for missing or offline devices.

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?

A single sentence front-loads the action and uses a colon to introduce a compact list of signal categories. There is no filler, repetition, or unnecessary elaboration.

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?

For a low-parameter, read-only tool with full schema coverage, strong annotations, and an output schema, the definition is mostly complete. The only notable gaps are the lack of explicit routing to historical-data alternatives and any caveat about data freshness or latency, but these are minor for an agent making a basic data-fetch call.

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?

Schema description coverage is 100%: both required parameters, device_sn and device_type, have clear descriptions including the allowed device-type values. The tool description adds no parameter-level detail beyond what the schema already provides, so the baseline score of 3 is appropriate.

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?

Description opens with a specific verb and object, 'Get the latest real-time reading', and enumerates the key data categories returned: PV power, load, grid import/export, battery SOC, temperatures, faults. This clearly distinguishes it from siblings like get_device_history (history vs latest) and get_device_info (metadata vs readings).

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 phrase 'latest real-time reading' clearly signals a current-snapshot use case, implying that historical data belongs to get_device_history. However, it does not explicitly name alternatives or state when not to use this tool, so it stops short of providing full routing guidance.

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