performance_start_trace

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

With no annotations provided, the description carries the burden of disclosure. It explains that the tool records profiling data to a .utrace file and that stopping auto-loads for analysis. Missing details include whether it overwrites existing files, any prerequisites, or potential side effects on performance.

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 well-structured with a clear purpose statement, parameter details, and usage example. The channels list is somewhat extensive but necessary for clarity. It could be slightly more concise, but overall it is focused and front-loaded.

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 has only two optional parameters and an output schema exists, the description is complete. It explains the core functionality, parameter options, and the pairing with performance_stop_trace. No critical information is omitted.

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 description adds significant meaning beyond the input schema by explaining the purpose and behavior of both parameters. For file_path, it clarifies that an empty value auto-generates a path. For channels, it lists presets, individual channels, and provides a full example. This fully compensates for the 0% schema description coverage.

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 clearly states that the tool starts recording a performance trace from the Unreal Editor, specifies the data types recorded (CPU, GPU, frame timing), and the output file format (.utrace). It distinguishes itself from sibling tools like performance_stop_trace and performance_analyze_insight by positioning itself as the starting point.

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 description provides explicit guidance on when to stop the trace by calling performance_stop_trace and includes examples for channel presets. However, it does not explicitly state when to use this tool vs. alternatives or when not to use it, though the context implies it is the primary profiling start tool.

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