tab_new

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

Adds real context beyond the annotations: it blocks waiting for page load when a URL is given, and it mutates global state by making the new tab current so later page tools target it. That side effect and blocking behavior are not derivable from readOnlyHint=false/openWorldHint=true alone. Not a 5 only because there is no mention of failure modes (e.g., bad URL, load timeout).

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 tight sentences, each doing distinct work: what it does, how it behaves and what it returns, and which sibling to use instead. No 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?

No output schema exists, and the description compensates by naming the return values (tab id, title, URL) and explaining how to use the id downstream. For a one-parameter tab-creation tool this covers everything needed to call it correctly.

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 the https:// default and the omit-for-blank-tab behavior. The description's 'optionally at a URL' merely restates that, so 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?

States a specific verb and resource ('Open a new browser tab') plus the side effect that it becomes the current tab. It explicitly distinguishes itself from the sibling navigate, which handles changing pages of existing tabs.

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?

Gives the alternative explicitly: 'Use navigate instead to change the page of an existing tab.' It also names the follow-on tools (tab_select, tab_close, `tab` argument) so the agent knows where this tool fits in a workflow.

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