sim_open_url

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

No annotations are provided, so the description carries the full burden. It discloses that the tool opens URLs on a simulator and notes the prerequisite for URL scheme registration, but does not mention error behavior, side effects, or what happens if the URL scheme is not registered.

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 with no redundant information. The first sentence states the core function, the second provides usage context, and the third adds a prerequisite. Every sentence is necessary and well-structured.

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 simple URL opening tool with no output schema, the description covers the core behavior, use case, and a key prerequisite. It lacks details on error handling or return behavior, but given low complexity, it is mostly complete.

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% with both parameters already documented in the input schema. The description adds no additional semantic information about the parameters beyond what the schema provides, so baseline 3 is appropriate.

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?

Description clearly specifies the action (Open a URL or deep link) and the target (on a simulator). It distinguishes from siblings like sim_launch_app and ui_tap by stating it's for app navigation via URLs, which is unique among the listed tools.

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 explicit usage context: 'Use this for app navigation — simctl does not support direct tap/swipe' and a prerequisite: 'The app must register the URL scheme in its Info.plist.' It does not explicitly mention alternatives or when not to use, but the context of siblings implies it.

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