system_get_frontmost_app

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

Annotations already declare the full safety profile (readOnly, idempotent, openWorld, non-destructive), so the description is not the burden-carrier here. It does add one piece of non-annotation context, '[permissions: none]', which usefully tells the agent no authorization is needed; the NSWorkspace mention is implementation detail rather than agent-relevant behavior.

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?

A single front-loaded sentence plus a short bracketed metadata tag; nothing is buried and nothing is wasted. The version/permission tag is arguably clutter, but it carries real information.

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?

With an output schema present, the return contents need no prose, and with zero parameters there is no input surface to document. The description plus rich annotations and a defined output shape cover everything needed to invoke this tool correctly.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. The description correctly avoids inventing argument semantics that do not exist.

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 gives a specific verb ('Read') and a precisely scoped resource ('frontmost application metadata'), which separates it from system_list_apps (all apps) and system_get_active_window (windows). It stops short of naming those siblings explicitly, so it is clear but not self-differentiating.

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?

There is no statement of when to use this tool versus system_list_apps, system_get_active_window, or system_activate_app. The agent must infer usage purely from the word 'frontmost' in the purpose line.

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