tab_open

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

With no annotations, the description carries the behavioral burden and does disclose the core side effect: a new tab is opened and navigated. It doesn't state whether the tab becomes active, how invalid URLs are handled, or what the tool returns, leaving some behavior implicit.

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?

One short sentence with no filler. The main action appears first, and 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?

For a one-optional-parameter tool with no nested schema, this is nearly complete: the action and URL parameter are covered. It falls just short of full completeness by not stating post-navigation behavior or return value, but the low complexity makes the gap minor.

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%, so the description doesn't need to document the url parameter; the schema already states the default about:blank. The description only reinforces the URL concept without adding new parameter semantics.

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 action ('Open a new browser tab') and destination ('navigate to a URL'). It distinguishes from tab_navigate by emphasizing a new tab rather than navigation in an existing context, though it doesn't explicitly name the alternative.

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 phrase 'new browser tab' implies use when a separate tab is needed, and the sibling name tab_navigate suggests the alternative for existing tabs. However, no explicit when/when-not guidance or exclusions are provided.

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