start_screencast

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

With no annotations, the description bears full burden for behavioral disclosure. It fails to mention that this tool starts an ongoing recording that must be stopped with 'stop_screencast', nor does it describe potential side effects like disk usage or system load. The description only lists parameter effects.

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?

The description is concise with a bulleted list of parameters, front-loading the main action. It wastes no words, but could add a brief sentence about the tool's lifecycle (e.g., 'Use stop_screencast to end recording').

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 that this tool initiates a background process, the description omits critical context: how to stop recording, that it produces files on disk, and any prerequisites (e.g., browser must be running). The output schema exists but does not offset the missing lifecycle information.

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?

The schema has 0% parameter description coverage, so the description compensates well. It explains four of five parameters: 'fmt' (jpeg vs png), 'quality' (0-100, JPEG only), 'max_width' (downscaling), and 'every_nth_frame' (capture frequency). The 'output_dir' parameter is only mentioned in the first line and lacks explanation of default behavior.

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 'Begin recording screencast frames to output_dir', which clearly communicates the action of starting a recording. The name and first line distinguish it from sibling tools like 'screenshot' (single capture) and 'stop_screencast' (stopping). However, it does not explicitly clarify that this starts a continuous capture process.

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?

No explicit guidance is provided on when to use this tool versus alternatives like 'screenshot' or when not to use it. There is no mention of prerequisites or contexts, leaving the agent to infer usage solely from the description.

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