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

Annotations already declare readOnly/idempotent/openWorld=false, so the safety profile is covered. The description adds genuinely useful output context: each entry carries a device_uid usable with device_summary and a url to an interactive history page, which goes beyond the annotations.

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?

Three sentences, front-loaded with the metric definition, then filters, then output affordances. Each sentence carries information, though the 'champions of staying powered on' flourish is slightly decorative.

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?

An output schema exists, so return-value explanation isn't required, yet the description helpfully points at device_uid and the url. With full parameter coverage and clear metric scoping, 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?

Schema description coverage is 100%, so brand, model, and limit are already fully documented with defaults and ranges. The description only restates that brand/model are optional filters, adding no syntax or matching nuance beyond the schema (e.g., the case-insensitive behavior is only in the schema).

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 with the exact metric ('longest single uptime ever recorded between reboots (max_elapsed_time)'). This precisely distinguishes it from the close sibling top_devices_by_live_uptime, which ranks on live uptime rather than a historical max.

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?

Provides a use case ('find which physical phones are champions of staying powered on') and notes that brand/model filters are optional. However, it never names an alternative or states when NOT to use this tool, which matters given the sibling top_devices_by_live_uptime and device_ranking.

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