Fill Form

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

The description adds context beyond annotations by explaining the targeting mechanism (same as operagx_click), the optional submit behavior, and the return structure. Annotations already indicate destructive/read-only, and the description complements rather than contradicts them.

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 with sections for args, returns, and examples, and every sentence contributes. It is front-loaded with the core purpose and remains informative without being bloated.

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?

Despite the tool's complexity (6 parameters, multiple targeting strategies, optional submit), the description covers all essential aspects: parameters, return format, examples, and alternatives. The output schema further enriches the context, so nothing critical is missing.

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 coverage is 100%, so the baseline is 3. The description adds value by explaining how the fields array works, the targeting options (elementId/selector/x+y), and provides meaningful examples. It goes beyond repeating schema descriptions.

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 'Fills multiple fields in one call and optionally submits at the end,' which is a specific verb+resource. It also distinguishes itself from siblings by explicitly mentioning operagx_click targeting and contrasting with operagx_type_text for single-field cases.

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 provides explicit when/when-not guidance: 'Use when: log in with username tomsmith and password foo' and 'Don't use when: only one field needs filling — operagx_type_text is simpler.' It also references relevant sibling tools like operagx_map_elements and operagx_click.

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