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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds that it returns linkUrl + sessionId and that it requires polling, which is useful behavioral context. However, it does not disclose details like whether a browser window opens automatically, how long the link is valid, or what happens on cancellation.

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?

Three sentences with no waste. The core action is front-loaded, the return values are stated, and the next step is given. 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?

For a parameterless tool with an output schema and annotations covering safety, the description is nearly complete. It explains the purpose, the return values, and the required follow-up polling. The only minor gap is not explaining how this differs from ucode_login_start, but the sibling list and the 'in-card button' title provide enough context.

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 0 parameters, so the schema provides no parameter documentation. The description compensates by explaining the return values (linkUrl + sessionId) and the follow-up action (poll ucode_login_poll), which is sufficient for a parameterless tool.

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 ('Starts browser sign-in') and resource ('visual card Connect button'), and distinguishes it from the sibling ucode_login_start by noting it is the in-card button variant. It is clear but does not fully explain how it differs from ucode_login_start beyond the UI context.

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 gives a clear usage context: it is for the visual card Connect button, and it explicitly instructs to poll ucode_login_poll until linked. It does not explicitly state when not to use it or name alternatives like ucode_login_start, but the polling instruction provides actionable guidance.

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