browser_upload_file

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

With no annotations, the description carries the full burden and does well: it discloses the side effect of clicking (native dialog), the path constraint (absolute, inside workspace), and the return behavior (updated page snapshot). It omits failure modes and whether pre-existing file selections are replaced, but the core behavioral profile is present.

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?

Four tight sentences: purpose first, then the click warning, then the path constraint, then return value and the untrusted-content note. Zero filler and each sentence adds distinct value.

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?

For a 4-parameter mutation tool with no annotations and no output schema, the description covers purpose, constraints, side effects, and return value adequately. Missing error/edge-case behavior (e.g., what happens if paths fall outside the workspace) keeps it short of a 5.

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 50% (only snapshot/screenshot carry descriptions), so the description must compensate for ref and paths. It adds real meaning for paths ('must be absolute and inside the VS Code workspace') and implies ref targets the file-input element, filling the schema gap for both required parameters.

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?

States a precise verb+resource ('Set the files of a file input') and adds the disambiguating hint that the snapshot renders it as 'file-input, possibly hidden'. An agent can immediately tell this apart from browser_click, browser_type, and browser_select_option.

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?

Gives clear conditional context (use it when the snapshot shows a file-input, including when hidden) and an explicit negative instruction ('Do not click the input: that opens a native file dialog'). It does not name a sibling alternative, but none of the sibling tools overlap, so the guidance is effectively complete.

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