login

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

No annotations were provided, so the description bears full responsibility. It fully describes the authentication flow, including differences based on client elicitation support, the PIN issuance behavior, the ~3-minute window, and the blocking nature of login_complete.

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 relatively long but well-structured, with clear breaks for client types and time-sensitive instructions. Every sentence adds necessary context, though it could be slightly more concise.

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 no output schema, the description adequately covers the return behavior (PIN or none needed), the blocking semantics, and the time window. It also explains prerequisites and next steps, making the tool's usage self-contained.

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 input schema already covers both parameters (phone, region) with descriptions. The description adds value by explaining when to include or omit them (prompting vs. reuse), which is helpful context beyond the schema.

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 is for logging in to LINE via passwordless secondary-device flow, using a specific verb ('Log in') and resource ('LINE'). It distinguishes itself from siblings like login_complete by explaining the two-phase flow.

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?

Explicitly explains when to use this tool versus login_complete, provides prerequisites (primary phone setting), and gives precise instructions for different MCP client types, including a warning not to wait on login_complete.

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