tab_select

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

With no annotations, the description carries the burden of behavior and does disclose an important rule: url_contains selects the first matching tab. However, it does not explain what happens when no tab matches, or what the default index -1 means when no args are provided, which are meaningful behavioral gaps.

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?

A single sentence that front-loads the main action and packs both selection modes without filler. Every word contributes to understanding 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?

This is a low-complexity tool with complete schema documentation, so the description does not need much. Still, the missing explanation of default index -1 behavior and no-match handling leaves the agent without full guidance for edge-case calls.

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 description coverage is 100%, so the baseline is 3. The description adds the 'first tab whose URL contains' rule, but this duplicates the schema's parameter description and adds little new semantic value beyond it.

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 action (switch to), a distinct resource (an existing browser tab), and both selection modes (index or url_contains). This clearly distinguishes it from tab_new, tab_list, and tab_close siblings without needing to name them.

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 description communicates that this tool is for activating an existing tab, which is clear context for when to reach for it. It does not explicitly exclude alternatives or list when-not-to-use, but the intended use is obvious from the action and sibling set.

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