fill_form

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

The description adds performance characteristics (faster, more reliable) but doesn't disclose side effects like partial failures or state changes. With only readOnlyHint=false in annotations, it provides modest additional context, but not enough for a higher score.

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 two sentences plus an example, concise and front-loaded. No wasted words.

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?

The description adequately covers the core usage scenario and provides guidance. It doesn't explain return values or includeSnapshot behavior, but the schema covers the parameters. Given the tool's moderate complexity, it is reasonably complete but could acknowledge response handling.

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 schema already provides full descriptions for all parameters, so the description doesn't need to add much. The example 'Fill username, password, and check Remember Me' illustrates usage but doesn't add new semantics 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 'Fill out multiple form elements at once', with a specific verb and resource, and distinguishes from sibling tools like 'fill' and 'click' by emphasizing the batch capability. The example further clarifies the scope.

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 instructs to 'ALWAYS prefer this tool over multiple individual fill or click calls when interacting with forms', naming the alternatives and the condition. It also explains why (faster, reliable, reduces turn count). However, it doesn't state exclusion cases, so not a perfect 5.

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