List Spaces

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, covering the safety profile. The description adds front-window scoping, the fact that pinned tabs are excluded from space counts, and the reconciliation formula (tabsInSpaces + topAppCount = totalTabs). This goes beyond annotation coverage, providing useful behavioral context, though it doesn't describe the exact return structure.

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 three sentences, front-loaded with the core purpose, followed by two concise clarifying details. No redundant or vague phrasing.

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 zero parameters and no output schema, the description provides sufficient context: what it returns (tab counts, active indicator), the window scope, reconciliation with pinned tabs, and the relationship to list_tabs. An agent can call it correctly and interpret results without additional information.

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 no parameters (input schema is empty), so there is nothing for the description to add. Baseline of 4 for zero-parameter tools is appropriate.

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 (list), resource (Arc spaces), and scope (front window), and adds tab counts and which space is active. It explicitly differentiates from list_tabs by noting the window coverage ('Counts cover the front window only, while list_tabs covers every window'), making the purpose unambiguous.

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?

It explicitly contrasts with list_tabs ('Counts cover the front window only, while list_tabs covers every window'), giving a clear selection rule. It also explains the reconciliation logic for pinned tabs (topApp), helping the agent decide when this tool's output is appropriate.

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