Starts recording a screencast (video) of the target page and saves it as an MP4 file.
Starts recording a screencast (video) of the target page and saves it as an MP4 file.
| Name | Required | Description | Default |
|---|---|---|---|
| file_path | Yes | Absolute or relative file path to save the MP4 video (e.g. 'recording.mp4'). |
Changes observed during successful MCP inspections.
v0.10.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden, yet it omits the critical lifecycle detail that recording continues until browser_screencast_stop is called and when the MP4 is actually written. It also doesn't state overwrite behavior, whether the path is relative to a configured download directory, or the effect on an already-running recording.
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 well-formed sentence with zero filler, front-loading the action and the resulting artifact. It could have absorbed the stop-pairing caveat without becoming bloated, but there is no padding to penalize.
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 one-parameter tool the description is thin: it never explains that starting a screencast requires a later stop call to produce the file, nor where a relative path resolves. With no annotations and no output schema to fill those gaps, the definition is not sufficient for correct 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?
Schema description coverage is 100% and the schema already supplies the path format and an example ('recording.mp4'). The description adds no syntax or resolution details beyond what the schema provides, so the baseline 3 applies.
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 ('Starts recording') plus resource ('screencast (video) of the target page') and names the output artifact (MP4 file). It is clearly distinct from most siblings, though the pairing with browser_screencast_stop is implied by naming convention rather than stated.
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?
There is no when-to-use guidance, no prerequisite call mentioned, and no referral to the obvious alternative browser_screencast_stop that must eventually be invoked to finalize the recording. The agent is left to infer the start/stop lifecycle entirely.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.