start_login

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

Beyond the annotations, it discloses important behavior: the returned link expires after about 60 seconds, must be shown immediately, and only one login runs at a time. These are operationally critical details an agent would not infer from readOnlyHint/openWorldHint/destructiveHint alone.

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 front-loaded with the core action and return value, then layers on expiry, concurrency, and call-context constraints. Every sentence carries actionable information without waste.

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?

With no output schema, the description appropriately states that it returns the device link and explains its short expiry. It also covers the concurrency limit and when the tool should be invoked, making it complete for a zero-parameter login-initiation tool.

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 parameter semantics are inherently minimal and the baseline is 4. The description does not need to explain any arguments.

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 names a specific action and resource: start a certificate login or early renewal, returning a device link. It is clear what the tool does, though it does not explicitly differentiate from the related access_status sibling.

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 gives explicit call conditions: only when answering a message from the human, and not from cron, /loop, or stop-hook turns. It also notes that only one login can run at a time, which further scopes correct invocation.

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