Device status (read-only)

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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered; the description adds a genuine contract beyond that: "Never raises: a field that cannot be read is reported with source unavailable." That partial-failure behavior is the key thing an agent needs, though it says nothing about freshness/caching of the snapshot or cost of the call.

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?

Front-loaded with the resource and its fields, then usage triggers, then exclusions, then the failure contract and return keys. Every clause carries routing or behavioral information; there is no restatement of the name or title.

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?

No output schema exists, and the description compensates by naming the return shape `{battery, storage, arch, memory}` plus the degraded-value convention. Combined with the annotations and an empty input schema, an agent has everything needed to call it correctly.

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?

Zero parameters, so there is nothing to disambiguate and the baseline is 4. The description correctly signals a no-argument call by framing the tool as a snapshot rather than implying any query/filter options.

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?

States a specific verb and resource ("read-only snapshot of the host hardware and OS") and enumerates exactly which fields it covers: battery, storage, CPU architecture, memory. It explicitly separates itself from `server_health`, `resolve_path`, and `path_adapter`, so an agent can pick it without opening any schema.

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?

Gives concrete when-to-use triggers tied to the agent's task ("free space before a download, battery before a long job, arch before picking a binary") and an explicit when-not clause naming all three siblings with their distinct scopes. Nothing about routing is left to inference.

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