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

Annotations already declare the safe read-only, idempotent profile, but the description adds two things annotations cannot: the absence of a session prerequisite (a setup/auth constraint) and the caveat that the `raw` registry is misleading (temperature in hundredths of a degree, multiple ambiguous 'capacity' keys). It stops short of 5 only because nothing is said about latency, failure modes, or when raw would be needed.

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, zero filler: the capability and returned fields come first, the session-free note second, and the summary-vs-raw warning last. Every sentence carries information an agent needs.

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 carries the return-value burden and does so: it lists the summary fields and warns about the raw payload's traps, and it clarifies the session prerequisite. Nothing essential for calling this tool correctly is missing.

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 coverage is 100%, so both parameters are documented in the schema, setting the baseline at 3. The description goes beyond it by explaining the interpretive consequences of `raw=true` (hundredths-of-a-degree temperature, ambiguous capacity keys) and by pointing the agent at `summary` as the value to read — genuine added meaning.

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 ('Get battery status of an iOS device') and enumerates the exact fields returned (charge percent, temperature in both units, charging state, health, cycle count), so the agent knows precisely what it gets. The 'iOS' qualifier cleanly separates it from the Android-oriented device_battery sibling.

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?

Explicitly says 'No automation session required', which is meaningful routing guidance in a toolset where most siblings need a session. It does not, however, name an alternative (e.g. device_battery for Android) or state exclusions, so it stops short of full when/when-not guidance.

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