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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the default range when omitted (1h), the meaning of 'Waiting' as measured wall-time percentage, and the null semantics where the host lacked complete same-run readings. Return shape and pagination/aggregation behavior are not covered.

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 dense sentence that front-loads the metric list and the range option, then appends the two caveats (default range, waiting/null semantics). It is efficient, though the run-on structure makes the trailing caveats easy to skim past.

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?

With no output schema, the description does the work of enumerating return content and the 'latest reading' inclusion plus null semantics. For a read-only two-parameter metrics tool with annotations covering safety, this is close to complete; only the response structure/series format and the id target are left implicit.

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 0%, so the description must carry parameter meaning. It fully documents the range parameter including the default ('1h when omitted'), which the schema does not encode. The id parameter is only implied ('A sandbox's...') and never states that it is the sandbox UUID required to identify the target.

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 enumerates the specific resource (a sandbox) and the exact measured quantities returned (CPU percent/cores, resident memory, CPU wait, memory stalls, disk use, disk I/O, network per second). It is unambiguous what the tool returns, though it omits an explicit verb like 'get' and does not name the sibling it differs from (e.g. runtime_sandboxes_inspect).

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?

It states an intended purpose ('to size a sandbox or find what drove a bill'), which implies when to reach for it. However, it names no alternatives and gives no when-not guidance, so an agent must still infer how this differs from runtime_sandboxes_inspect or runtime_sandboxes_list.

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