login

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

With no annotations, the description carries full behavioral burden. It explains credential sources and selector auto-detection, but omits important traits like side effects (e.g., navigation after submission), error handling, or what happens if both credential modes are provided. It's adequate but not comprehensive.

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 well-structured: purpose first, then credential options, selector behavior, and a navigation prerequisite. Every sentence is informatively dense with no fluff, earning 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?

Given the tool's complexity (6 params, 0 required, no schema descriptions) and no annotations, the description covers essential aspects: credential modes, selector fallback, and navigation prerequisite. The output schema exists, so return values are covered elsewhere. Minor gaps like conflict resolution remain.

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?

Schema description coverage is 0%, so the description compensates by explaining the two credential modes (site vs username/password) and the selector auto-detection logic. It adds meaning to the parameters without listing each one, but effectively ties them to usage patterns.

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 function: 'Fill a login form and submit it.' It specifies the resource (login form) and the action (fill and submit), distinguishing it from generic fill_field or submit_form tools by focusing on login-specific behavior and credential handling.

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 context: 'Use navigate() to go to the login page first' and explains credential options (site OR username/password). It doesn't name alternatives explicitly but implies the tool is for login forms, which is sufficient guidance given the sibling list.

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