Start Promise login (browser)

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

With no annotations provided, the description carries the burden. It discloses key behaviors: starts a local callback server, opens the default browser, and returns a URL as a fallback. However, it does not mention potential failure modes (e.g., callback timeout, user cancellation) or side effects on existing sessions. Still, it goes beyond a minimal statement.

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 concise, front-loaded with the core action, and every sentence adds value. It covers the mechanism, the fallback, the user interaction, and the next step without fluff.

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 zero-parameter tool with no output schema, the description is remarkably complete: it explains the flow, the returned URL as a fallback, and the required follow-up. The only minor gap is not specifying what happens on failure or cancellation, but that is an edge case for a login starter.

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, so the input schema is empty and coverage is 100%. Per the rubric, a baseline of 4 applies for 0-parameter tools. The description adds no parameter meaning because there are none to explain, which is appropriate.

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 ('Begin logging in') and resource ('persistent Promise identity'), and clarifies the mechanism (local callback server + browser). It distinguishes itself from the sibling promise_login_finish by explicitly saying to call that tool afterward, and from raw token pasting by recommending against it.

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?

It provides when-to-use instruction (starting a login), explicitly names the follow-up tool (promise_login_finish), and gives a recommendation against an alternative method (raw id_token). This is clear and actionable for an agent deciding how to initiate login.

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