fill_form

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

Annotations already indicate write (not readOnlyHint), non-destructive (destructiveHint false), and potential side effects (openWorldHint true). The description adds targeting behavior (active tab vs. specific browserId) but lacks details on error handling, field matching, or whether the page is waited for.

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?

Two sentences, front-loaded with purpose. No wasted words. Efficiently communicates core function and key parameter behavior.

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 and simple tool, the description is nearly complete. It covers purpose, fields syntax, and targeting. Could mention that it does not submit the form, but that is implied by sibling tool 'submit_form'. Minor gap in describing return behavior.

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 covers 100% of parameters with descriptions. The description adds context about 'fields' using CSS selectors/names, but the schema already provides a similar example. The targeting note for 'browserId' paraphrases the schema description without new semantics.

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 verb ('fill'), resource ('multiple form fields'), and scope ('at once'), distinguishing it from sibling tools like 'type_text' which handle single fields, and 'submit_form' which submits.

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 implies usage for filling multiple fields simultaneously (vs. one at a time) but does not explicitly state when not to use or compare to alternatives like 'type_text' or 'set_checked'. No exclusion criteria are given.

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