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

No annotations are provided, so the description carries the full burden. The 'Check' verb implies a read-only operation, and the session requirement is genuine behavioral context beyond the schema. However, it doesn't disclose failure behavior when no session is active or what the tool returns, both of which would matter given zero annotation coverage.

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?

Two short sentences with the purpose front-loaded and the prerequisite following. There is zero filler; every word contributes either to what the tool does or when it can be used.

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 one-parameter status check, the core is covered: purpose and precondition are explicit. But with no output schema, the return value (e.g., a boolean) is undefined, and the behavior when no active session exists is unstated. Adequate but with clear gaps given the lack of annotations.

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% — the udid parameter is already documented as 'iOS device UDID' in the schema. The description adds no parameter-level meaning, so the baseline of 3 for high schema coverage applies.

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 states a specific verb and resource: 'Check if an iOS device screen is locked.' This is unambiguous and naturally distinguishes it from sibling ios_unlock, which changes lock state rather than querying it. An agent can tell them apart from name and description alone.

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 description gives a clear, explicit precondition for use: 'Requires an active iOS automation session.' This is the key contextual guidance an agent needs before invoking the tool. It stops short of 5 because it doesn't name alternatives or exclusions (e.g., directing an agent to ios_unlock when the goal is to change state rather than check it).

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