apple_safari_navigate_tab

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

Annotations already declare the dangerous, non-idempotent, open-world profile, so the safety bar is lower. The description adds real value beyond them by disclosing the race-condition hazard (indices shift, wrong tab could be modified), which is not encoded in any structured field. It does not mention permissions or success/return behavior, so a 4 rather than 5.

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 sentences, zero filler, with the action stated first and the safety precondition immediately after. Every clause earns its place.

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 destructive, non-idempotent mutation with no output schema, the description supplies the key correctness guard and the annotations supply the safety profile. Remaining gaps (window/tab addressing semantics, return behavior) are minor and largely inferable from parameter names.

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 0%, so the description carries the burden. It explains the critical expectedUrl parameter ('its previously observed URL') and the url target, but leaves windowId and tabIndex undocumented beyond their self-evident names. Partial compensation, not full.

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 (Navigate) and resource (one Safari tab) plus the destination type (HTTP(S) URL). An agent can distinguish it from apple_safari_open_tab, close_tab, get_tab, and list_tabs by the action alone, without opening any schema.

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 second sentence gives a clear precondition: it requires the previously observed URL and explains the failure mode it prevents (index shift causing a different tab to be modified). It does not name an alternative tool or state exclusions, so it stops short of a 5, but the when-to-use context is genuinely useful.

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