Close Tab

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

Annotations already flag destructiveHint=true and idempotentHint=false, but the description adds genuinely new behavioral facts: the call is refused outright if the agent has not opened a tab, the user's tab is never a fallback target, closing is irreversible, and tab ids are not reused. These are exactly the failure modes an agent needs before invoking a destructive tool.

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?

Four short sentences, each load-bearing: what it does, the implicit-tab rule and its refusal condition, the explicit-id path, and the irreversibility/id-reuse facts, closing with the preferred alternative. Front-loaded and zero filler.

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?

For a single-optional-parameter destructive tool with no output schema, the description covers the implicit-vs-explicit targeting rule, the safety guarantee about the user's tab, irreversibility, and the sibling alternative. Nothing needed to call it correctly is missing.

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% and the schema description already explains that omitting tab_id uses the agent's current tab. The description reinforces this and adds the 'pass this or call open_url first' guidance, but most of the parameter meaning is already carried by the schema, so the baseline 3 applies.

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?

Specific verb (close) plus resource (one tab), and it immediately distinguishes the two modes of operation: implicit own-tab vs. explicit tab_id. An agent can differentiate this from siblings like close_own_tabs and switch_to_tab without reading any schema.

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?

States exactly when to omit tab_id, when to pass an explicit id from list_tabs, and names the preferred alternative (close_own_tabs) for cleanup with the condition that selects it. Exclusions are explicit: it will never close the user's visible tab.

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