close_tab

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

With no annotations, the description carries the full burden; it discloses a non-obvious edge case (closing the last tab depends on the user-data-dir), which is genuinely useful context. However, it never warns that closing may discard unsaved state or explain what 'depends on the user-data-dir' actually means, leaving key destructive-behavior consequences unstated.

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 short sentences, front-loaded with the action and immediately followed by the default behavior. The vague trailing clause about user-data-dir is the only weak spot but still carries information.

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 one-optional-parameter tool with no output schema, the description covers the primary action, default behavior, and a boundary case. What an agent needs to call it correctly is present; only failure/return behavior is left implicit.

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 single parameter already documents 'Tab to close. Omit to close the active tab.' The description restates that same default rather than adding new semantics beyond 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?

The description states a specific verb and resource ('Close a tab'), which clearly contrasts with siblings like new_tab, switch_tab, and list_tabs. It does not explicitly name an alternative, but the action is 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 explains the default invocation ('If no targetId is given, closes the active tab'), which tells the agent how to call it in the common case. There is no explicit guidance on when not to use it or which sibling to prefer if the intent is to simply change focus.

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