ios_open_url

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

Annotations already declare the mutation/open-world/idempotent profile (readOnlyHint=false, openWorldHint=true, idempotentHint=true, destructiveHint=false). The description adds only routing advice, not behavior such as what happens on an invalid or unsupported scheme, whether it foregrounds the app, or failure handling. Useful but not rich beyond the annotations.

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, purpose front-loaded, no wasted words. The efficiency claim in the second sentence earns its place as decision guidance.

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 tool with an output schema, annotations covering safety, and a fully documented param, the definition is nearly complete. The only gap is failure/fallback behavior when a deep link cannot be opened.

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% and the single url parameter already carries its format examples and the iOS 26 Settings caveat, so the description adds nothing beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Open a URL or deep link'), and the second sentence distinguishes it from the tap-through navigation siblings. It never names an adjacent tool (e.g. ios_launch_app) outright, so sibling discrimination is implied rather than explicit.

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?

Gives a clear usage preference: use this as the cheapest route to a screen instead of tapping through navigation. There is no explicit when-not case (e.g. what to do if the deep link fails or is unsupported).

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