ui_session_start

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

With no annotations provided, the description must fully disclose the tool's behavior. It only states 'Start a Playwright browser session' but does not mention side effects (e.g., launching a browser, consuming resources), whether it requires a base URL or specific configuration, or what the session represents. This lack of detail leaves the agent without critical behavioral context.

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 a single concise sentence with no redundant wording, earning credit for brevity. However, it is under-specified for a tool with 5 parameters and no annotations, making the brevity a shortcoming rather than a quality. It communicates the core action but omits essential details, so it is acceptable but not well-structured.

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 the tool's 5 optional parameters, no annotations, and no output schema, the description is insufficient. It does not explain what the tool returns (e.g., a session handle), how the parameters affect behavior, or any setup requirements. This is a critical gap for an agent attempting to invoke the tool correctly, making the description incomplete.

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 0% and the description makes no mention of any parameters (baseUrl, headless, slowMoMs, viewportWidth, viewportHeight). Since the description is solely responsible for explaining parameter meaning, its complete omission fails to add value beyond the raw schema field names, leaving the agent without guidance on parameter values or relationships.

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 uses the specific verb 'Start' with the resource 'Playwright browser session', clearly indicating the tool's action. It distinguishes itself from sibling UI tools like ui_session_stop and ui_navigate, which operate on an existing session. However, it could be slightly more specific about the session's scope or purpose beyond generic 'UI automation'.

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 guidance on when to use this tool versus alternatives. It states 'for UI automation' but does not mention prerequisites (e.g., prior session state), exclusions, or when to prefer sibling tools like ui_navigate or ui_action. The description leaves the agent to infer usage context without explicit direction.

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