open_url

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

Annotations already indicate readOnlyHint=false, so the mutation aspect is known. The description only says 'opens a URL', which adds minimal behavioral context. It does not disclose potential side effects like launching an app or requiring a booted simulator, but with annotations covering the safety profile, the added value is limited yet not absent.

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?

The description is a single, well-structured sentence that front-loads the action and communicates the key use case. It contains no fluff or redundant information, making it exceptionally concise.

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 tool with two params and no output schema, the description is largely sufficient. It explains the purpose and use case, and the schema covers parameters. It lacks explicit mention of preconditions like a booted simulator, but given the surrounding tools (e.g., get_booted_sim_id) and simplicity, the omission is minor.

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%, with both 'url' and 'udid' already documented in the schema. The tool description does not add any additional meaning beyond what the schema provides, so the baseline score of 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?

The description uses a specific verb 'Opens' and resource 'URL in the iOS Simulator', clearly differentiating from sibling tools like launch_app (which launches an app) and open_simulator (which opens the simulator app). It also states the intended use case (testing deep links and universal links), fully clarifying the tool's purpose.

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 provides clear context by mentioning it is useful for testing deep links and universal links, implying when to use it. However, it does not explicitly name alternatives or state when not to use it, stopping short of full exclusion guidance.

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