start_login

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

With no annotations, the description carries the full behavioral burden. It usefully discloses an isolation guarantee ("no other browser profiles or cookie contents are read"), but omits what start_login itself returns, QR lifespan/expiry behavior, and error or retry conditions.

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?

Short and front-loaded: the core action comes first, followed by the scanning behavior and the follow-up call. The final privacy clause is a semicolon-joined aside that borders on clutter but still 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?

For a no-parameter, no-annotation, no-output-schema tool, the description covers the start-to-poll workflow and isolation scope but leaves the return value of start_login undefined — an agent cannot tell whether it receives a QR image, a path, or a session handle. Adequate but with a clear gap.

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 takes zero parameters and the schema is empty, so there is nothing for the description to disambiguate. Baseline 4 applies since the description doesn't need to compensate for any parameter semantics.

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 ("Prepare a dedicated local Douyin login QR"), which is clearly distinguishable from siblings like check_creator or get_report. It also names login_status as the companion call, though it doesn't explain what "dedicated local" means relative to other possible login flows.

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 clear next-step guidance by naming login_status for polling the image path, and "User scans normally" sets expectations for the human-in-the-loop flow. It stops short of stating when-not to use it or any prerequisites (e.g., existing session handling).

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