fill_form

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

The description discloses precise action semantics: fill/select replace, type appends, check treats true-like values as ticks and clears otherwise. It also explains how intents resolve against page elements and what the return value is. This adds significant behavioral detail beyond the annotations' readOnlyHint/destructiveHint flags, without contradicting 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 dense but each sentence earns its place, moving from high-level purpose to parameter format to action semantics to return/error handling. It is not overly verbose, though it could be slightly better structured with explicit examples or bullet points. Still, it remains readable and compact for the amount of behavior it documents.

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 covers the only parameter's structure, all action behaviors, return shape, and error case. It does not include a concrete JSON example, which would help, but given the complexity is moderate and the output schema reportedly exists, the description is largely complete. The openWorldHint could be expanded but is not critical for invocation.

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?

With 0% schema description coverage, the schema only states 'fields_json' is a string. The description fully compensates by defining the JSON list format, each field ({selector|intent, value, action?}), the action defaults, and the semantics of each action. This is essential meaning that the schema alone cannot convey.

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 explicitly states a specific verb and resource: 'Fill several fields in one call.' It then defines the exact JSON structure and supported actions, making the tool's purpose unambiguous. No sibling tool has a similar batching/fill behavior, so the purpose is well distinguished.

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 phrase 'Fill several fields in one call' implies when to use it (when multiple values need to be set together) but it never names alternatives or exclusion conditions. There is no mention of press_key, upload_files, or other sibling tools that could handle similar tasks, leaving the agent to infer the boundary.

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