Identify performance issues in Three.js scenes by recording FPS and frame times for a set duration, returning averages, percentiles, spikes, and jank.
[INSPECT] Read-only. Record FPS and frame times for N seconds: avg/min/max, percentiles, spikes, jank.
| Name | Required | Description | Default |
|---|---|---|---|
| duration | No | Seconds (default: 3, max: 30) | |
| includeFrameTimes | No | Include raw frame times (default: false) |
Changes observed during successful MCP inspections.
v0.5.0Input schema / additionalPropertiesRemoved value: -falseInput schema / properties / duration / descriptionPrevious value: -"Recording duration in seconds (default: 3, max: 30)"New value: +"Seconds (default: 3, max: 30)"Input schema / properties / includeFrameTimes / descriptionPrevious value: -"Include raw frame times array (default: false, saves tokens)"New value: +"Include raw frame times (default: false)"v0.4.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, covering the safety and idempotency profile. The description repeats 'Read-only' (redundant) and adds what data is captured, but it does not disclose behavioral traits such as potential performance impact of recording or whether it blocks execution.
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 two sentences, front-loaded with a tag and read-only note, then the core action and output metrics. Every phrase earns its place with no redundancy or 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?
For a simple read-only tool with two optional parameters and no output schema, the description sufficiently explains what is recorded and what summary metrics are returned. It lacks usage context relative to siblings, but the core information an agent needs to invoke it correctly is present.
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 both parameters (duration, includeFrameTimes) are fully documented in the schema with defaults and max. The description mentions 'for N seconds' and 'frame times' but adds no syntax or format details beyond what the schema already provides, so the baseline of 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 ('Record') and resource ('FPS and frame times') and lists the metrics captured (avg/min/max, percentiles, spikes, jank). It does not, however, distinguish this tool from siblings like performance_snapshot or draw_call_breakdown, leaving the agent to infer the difference.
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 gives no explicit when-to-use guidance or alternatives. The '[INSPECT] Read-only' tag implies it is a read operation, but there is no direction on when to choose this over performance_snapshot or other monitoring tools, nor any prerequisites or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.