browser_uploadAttach local files by absolute path to a file input or drop zone, supporting uploads up to 25 MB total through a live browser session.
Attach local files (absolute paths, 25 MB total) to a file input, or drop them onto a drop zone.
| Name | Required | Description | Default |
|---|---|---|---|
| ref | No | Element ref from browser_find or browser_capabilities. | |
| paths | Yes | ||
| tabId | No | ||
| selector | No | CSS selector, if you have no ref. |
Changes observed during successful MCP inspections.
v0.1.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It usefully discloses a size constraint ('25 MB total'), but omits other behaviorally relevant facts: what happens on success/failure, whether upload triggers automatically, and any permission or timing requirements. It adds real value but leaves meaningful gaps for a mutation tool.
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?
A single sentence that is front-loaded with the core action and constraint, with zero filler. Every clause (paths, size limit, file input, drop zone) earns its place.
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?
With no annotations and no output schema, the description must do more work. It covers the action and a key constraint but says nothing about outcomes, error handling, or how 'ref' is obtained (only deferred to the schema's mention of browser_find). Adequate but thin for a state-changing browser tool.
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%, so the description should compensate. It adds genuine meaning by requiring 'absolute paths' and the 25 MB total limit, which the schema does not state for the paths parameter. However, 'tabId' remains undocumented in both schema and description, leaving half the parameters under-specified.
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 specific verb (Attach) and resource (local files) and clarifies the two target contexts (file input or drop zone). Clear enough to distinguish from read-oriented siblings, though it does not explicitly name the inverse tool (browser_downloads) or other browser_* tools. The core action is unambiguous.
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 mention of 'file input' and 'drop zone' implies when the tool applies, giving the agent two usage scenarios. However, there is no explicit when-to-use vs when-not guidance and no alternatives are named, so usage remains inferred rather than directed.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.