Put tabs into a tab group

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

The annotation only says readOnlyHint=false; the description goes beyond that by identifying the native Firefox tab-group mechanism and, importantly, disclosing that the result is a real tab-strip group a human can collapse or reopen later — a persistent, user-visible side effect. It omits edge behavior such as what happens to tabs already in another group and what the call returns.

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 its resource, with the implementation reference and the UI consequence following. No filler, though the parenthetical API name is marginally more useful to implementers than to an agent choosing the tool.

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 mutation tool with only readOnlyHint=false, no output schema, and no destructive hint, the description covers intent and persistence well but leaves gaps: whether grouping removes tabs from prior groups, whether the created group's identity is returned (relevant since browser_remove_tab_group exists), and any failure conditions.

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 each of the three parameters is documented with descriptions plus an enum for color, so the schema carries the load. The description's "contexts required, label and color optional" restates the schema's required array rather than adding new semantics, 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?

States a specific verb and resource: "Create a tab group from the given tabs," naming the underlying implementation (gBrowser.addTabGroup). An agent can tell this makes a new group rather than mutating an existing one, though it never explicitly contrasts with the nearby browser_move_tab_to_group or browser_list_tab_groups siblings.

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?

"Give the tab context ids; label and color are optional" implies the calling convention, but there is no explicit when-to-use guidance, no statement of prerequisites (must the tabs be in the same window? must they be ungrouped?), and no named alternative for putting tabs into an existing group.

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