session_close_tab

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

Goes well beyond the annotations by disclosing that closing a tab is not undoable, that the active tab is the one the user is looking at, and that the T3rnel Browser extension is required while the standalone browser refuses the call. These details match and enrich the destructiveHint annotation.

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?

Three concise sentences that front-load the action and return value, then add essential caveats. Every sentence contributes meaningful information, from the id source to the irreversibility and environment restriction.

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 having no output schema, the description states the return shape. It also covers prerequisites, side effects, environment requirements, and the unique no-default behavior, making the tool fully actionable for a one-parameter destructive operation.

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 input schema already documents tabId as the tab to close from session_list_tabs, and the description primarily repeats that provenance. It adds the no-default context, but that is more behavioral than parameter-specific, so the schema-coverage baseline of 3 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?

States a specific verb ('Close'), a clear resource ('a tab'), and the required source of the identifier ('from session_list_tabs'). It also distinguishes itself from sibling tools by explicitly calling out that tabId is required and there is no active-tab default.

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?

Provides clear context by directing the agent to obtain the tab id from session_list_tabs and warns that this tool, unlike every other session tool, requires an explicit tabId. It does not explicitly name alternative tools or list exclusions beyond the active-tab contrast, but the guidance is sufficient for correct selection.

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