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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the auto-start behavior for the automation session and the returned value shape ('Returns the URL string').

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 short sentences with no filler; the core action is front-loaded and the return value and session precondition follow in order of importance.

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 single-parameter read tool with no output schema, the description covers the action, the returned value, and the session precondition. Only minor edge-case behavior (e.g., no active Safari tab) is left unspecified, which is acceptable at this complexity.

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?

Only one parameter (udid) with 100% schema description coverage, so the schema fully documents it. The description adds no semantics beyond 'iOS device' for that parameter, making the baseline 3 correct.

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 the current URL loaded in Safari) plus the platform (iOS device), and it states the return value. It reads clearly against mutation siblings like ios_navigate_url, though it does not explicitly name an alternative to route away from.

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 precondition ('Requires an active iOS automation session (auto-starts if needed)'), which is real usage context. However, there is no explicit guidance on when to use this versus ios_navigate_url or the Safari DevTools siblings; usage is only implied.

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