browser_tabs

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

Annotations already declare readOnlyHint=true, so the agent knows this is a safe read operation. The description adds the behavior of returning the active tab as the default when omitted, and explicitly lists the fields available. This is contextual information that the schema (empty) does not provide, and it aligns with the read-only annotation.

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?

The description is two sentences with no filler. The primary purpose is front-loaded, and the usage instruction follows immediately. Every clause earns its place, and the format is easy to parse.

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 simple listing tool with no parameters and no output schema, the description fully explains what is returned, the default behavior, and how to apply the result with sibling tools. Nothing an agent needs to call it correctly is missing.

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?

The tool has zero parameters, and the schema trivially covers 100% of them. The description appropriately focuses on output semantics rather than parameters, and it clarifies the default behavior (active tab) which is the only implicit parameter-like choice. Baseline for 0 parameters is 4, and the description does not need to add more.

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 clearly states the verb 'List' and the resource 'open tabs in the real browser', and enumerates the returned fields (id, title, url, active). This distinguishes it from sibling tools like browser_navigate or browser_act, which perform actions rather than listing. The mention of 'real browser' also adds a specific scope.

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 provides direct guidance on how to use the returned tab ids with other tools ('Use a tab id with the other tools to target a specific tab; omit to use the active tab'). While it does not explicitly state when to call this tool vs alternatives, the instruction implies it is the prerequisite for tab-targeting operations and is clear enough for an agent to infer its role.

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