performance_start_trace

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

The only annotation is readOnlyHint=false, so the description carries most of the behavioral burden. It never states that the trace must be captured then stopped/exported, that the page should be navigated first, or where the raw trace data goes (that context lives only in the schema parameter text, not the description). No behavioral traits beyond the annotations are disclosed.

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?

Two tight sentences, front-loaded with the action and then the motivation. Every clause earns its place with no filler.

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 output schema and only a single annotation, the description is adequate on purpose but thin on workflow: it does not mention the trace must be stopped (performance_stop_trace) and analyzed, nor the reload/navigation prerequisite. Sufficient to start a trace, but not complete enough for an agent to use the full trace lifecycle correctly.

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%, so the schema already documents pageId, reload, autoStop, and filePath fully, including the 'navigate first' prerequisite. The description adds no parameter meaning of its own, 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?

States a specific verb+resource ('Start a performance trace on the target webpage') and reinforces it with concrete use-case goals (Core Web Vitals: LCP, INP, CLS). It is clearly distinguishable from take_screenshot or evaluate_script, though it never names its counterpart performance_stop_trace, so the lifecycle pairing is left implicit.

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?

Gives clear usage context ('Use to find frontend performance issues... and improve page load speed'), telling the agent when this tool is appropriate. However, it names no alternatives (performance_analyze_insight, lighthouse_audit, performance_stop_trace) and provides no when-not guidance or prerequisites.

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