open_url

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

With no annotations, the description carries the full burden and does well: it discloses the two execution paths, that Safari may be started as a side effect, and the rough latency (~3 s vs. minutes). It omits failure modes and what happens to existing tabs or the current page state.

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 dense sentences, front-loaded with the action and its fallback; nothing is filler. The compressed phrasing ("No typing. typing=true types it...") is slightly terse but readable.

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 5-parameter tool with no annotations and no output schema, the definition leaves notable holes: timing/pacing parameters are unexplained, there is no mention of return value or error behavior, and no relation to the `navigate` sibling. Adequate but incomplete.

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 only 20% (only `page` is documented). The description meaningfully explains `typing=true` including its cost, which compensates for one gap, but `delay_s` and `timeout` are undocumented in both schema and description.

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 an address in Safari") and even discloses the two internal mechanisms used (inspector vs. SpringBoard). It does not distinguish itself from the sibling `navigate`, which an agent may reasonably consider interchangeable, so it falls short of a 5.

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 clear conditional context: the ~3 s inspector path applies when a page exists, otherwise SpringBoard starts Safari. It also contrasts the default no-typing behavior against `typing=true`, with an explicit cost warning ("minutes"). No guidance on when to prefer this over sibling `navigate`.

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