login_start

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

With no annotations, the description carries the behavioral disclosure burden. It transparently explains that the tool returns a URL+code, that login_complete will wait by polling, and that the agent should not wait for user confirmation. This is valuable context for correct sequencing. It could add fallback behavior (e.g., if user cancels or the code expires), but for a simple flow it is quite transparent.

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 extremely concise at two sentences. The first sentence states purpose and output; the second contains the critical sequencing instruction, clearly flagged with 'IMPORTANT.' Every word earns its place, and the structure front-loads the essential information.

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?

Given the tool's simplicity (no parameters, no output schema, no annotations), the description is fully self-contained. It covers what the tool does, what it returns, and the exact follow-up action (call login_complete). The agent has enough context to invoke the tool correctly and handle the next steps without additional information.

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 schema provides no parameter details. According to the rubric, a 0-parameter tool gets a baseline of 4. The description appropriately focuses on the tool's output and the immediate next action rather than parameter intricacies.

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 tool's purpose: 'Start the PostKing login flow.' It specifies the output ('Returns a URL and short code') and distinguishes itself from the sibling tool login_complete by focusing on the initiation step rather than the completion step.

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 explicit step-by-step guidance: show the URL+code to the user, then immediately call login_complete, explaining that it polls in the background. This is clear when-to-use context. However, it does not explicitly mention when not to use the tool (e.g., if already logged in) or compare it to other auth-related tools like whoami/logout.

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