Browser Tab Close

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

With no annotations, the description carries the burden of behavioral disclosure. It does disclose an important edge-case behavior: the active tab cannot be closed when it is the last tab. However, it does not explain what happens after closing a tab, how session relates to the operation, or how invalid indices are handled.

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 a single front-loaded sentence with no filler. The parenthetical adds a genuinely useful behavioral constraint without bloating the text. Every word 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?

Despite the tool's apparent simplicity and existing output schema, the description is not complete enough for correct invocation. The meaning of the required 'index' parameter and the optional 'session' parameter is entirely unexplained, and the relationship between the 'active tab' restriction and the index parameter is ambiguous.

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 needed to explain what 'index' and 'session' mean, but it does not mention either parameter. An agent is left to guess whether index is 0-based, which tab it targets, and what session scope applies. This is a significant gap because the schema itself provides only types and defaults, no semantic meaning.

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 uses a specific verb ('Close') and resource ('tab'), making the core operation unambiguous. It also adds a key constraint (the active tab cannot be the last one), which helps distinguish this from tab-list, tab-new, and tab-select siblings, though it does not explicitly state that closing is by index.

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 gives a clear context: use this when you need to close a browser tab. It also provides an exclusion by noting that the active tab cannot be closed if it is the last tab. It does not mention alternatives or prerequisites such as using browser_tab_list to obtain an index, but the intended use case is still fairly clear.

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