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 so richly: it names the mechanism (Chrome Debugger API, no dialog), the permission prerequisite, the error mapping ("Not allowed" reported as file-access-off), and the non-obvious cleared_by_page/seen_in_field post-upload behavior. This is well beyond a typical definition.

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?

Every sentence carries usable content, but the structure is not front-loaded: it opens with a browser-extension setting caveat and a long error-mapping sentence before stating the core action mid-paragraph. An agent scanning the first line learns about a toggle rather than what the tool does.

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?

There is no output schema, and the description compensates by explaining the relevant return semantics (ok with cleared_by_page and seen_in_field) as well as the failure signal (file-access-off). Prerequisites, constraints, alternatives and edge cases are all covered for this level of tool complexity.

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 schema documents file/files/selector including the file_path alias, establishing a baseline of 3. The description adds genuine semantics on top: files must be regular files inside the server's working directory, with folders, symlinks and hardlinks pointing outside refused.

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 states a specific verb and resource: "Upload a file to a <input type=\"file\"> element on the page." It further distinguishes itself from the sibling browser_drop_file by routing drag-drop zones without a visible input there, so an agent can pick the right tool without opening the schema.

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?

It gives explicit when-not-use guidance ("For drag-drop zones without visible file input use browser_drop_file") and surfaces the key precondition ("Allow access to file URLs" toggle, including that it also grants broader local-file page access). It also advises re-checking the page before re-attaching when the field is cleared, which is actionable selection guidance.

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