Global Privacy Control state

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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds meaningful behavioral context beyond that: this command exists only in Marionette, not BiDi, and requires the browser to be launched with --marionette, including the port source and default. It does not state the exact return format, keeping it from a 5.

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?

Two tight sentences: the first states what is read, the second gives the essential Marionette prerequisite. It is front-loaded and every sentence 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?

This is a zero-parameter read-only tool with no output schema, so the description does not need to explain parameters or return structure. It covers the purpose and the key environmental prerequisite, which is sufficient for an agent to invoke 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?

There are zero parameters, so the baseline is 4. The schema is empty and fully described; no parameter semantics are needed or expected.

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 verb and resource: read whether the browser sends the Global Privacy Control signal. It names the concrete header (Sec-GPC) and clearly distinguishes this getter from the sibling browser_set_gpc without needing to reference the sibling explicitly.

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 purpose makes clear this is a read-only check, and the NOTE gives an important usage condition: the browser must have been started with --marionette. It does not explicitly route agents to browser_set_gpc for mutation or mention when not to use it, so it falls short of a 5.

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