Open URL

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

The annotations only say the tool is not read-only and touches the outside world. The description adds meaningful behavioral details: Arc is launched if needed, new tabs target the agent space or main window, and Arc auto-selects new tabs, restoring the previous selection unless activate is passed. These non-obvious behaviors go well beyond the structured 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?

The description is compact, front-loaded with the core action, and every sentence adds useful behavioral context. There is no redundancy or filler, making it easy for an agent to parse quickly.

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?

Given 8 parameters, 100% schema documentation, and no output schema, the description covers the main non-obvious runtime behaviors: launching Arc, space routing, and tab selection. Combined with the richly documented input schema, an agent has enough context to select and invoke the 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?

Schema coverage is 100%, so the baseline is 3. The description adds extra semantic value by explaining the default space behavior and by clarifying why the activate parameter exists: the prior tab selection is restored unless activate is passed. This is more than the schema alone provides.

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 states a specific verb and resource: 'Open a URL in Arc.' It also adds important scope details such as launching Arc if needed, so an agent can distinguish this from tab-management and navigation siblings like reload_tab or switch_to_tab.

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 makes the core use case clear and gives context about where new tabs land, but it does not explicitly state when to prefer this tool over alternatives like reload_tab or wait_for_load. No when-not conditions or alternative names are given, so guidance is mostly implied.

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