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browser_performance

Evaluate web page performance by collecting metrics and comparing against budgets, or record full performance traces with HAR output.

Instructions

性能分析工具(v1.9.5 起合并 browser_performance_check/trace)。通过 mode 参数区分子模式:check(默认,采集当前页面性能指标并按预算评估)/ trace(记录完整性能轨迹并输出 HAR 和结构化数据)。

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlNo要追踪性能的目标 URL。如果不提供则使用当前页面(mode=trace 时使用)
modeNo性能模式:check(默认,采集性能指标并按预算评估)/ trace(记录完整性能轨迹)check
budgetsNo预算阈值,支持 domContentLoaded、load、fcp、lcp、cls、longTaskCount、resourceCount、slowRequestMs(mode=check 时使用)
durationNo追踪持续时间(毫秒),默认 5000(mode=trace 时使用)
exportHarNo是否导出 HAR 格式数据,默认 true(mode=trace 时使用)
categoriesNo要记录的性能类别,默认 ["navigation","resource","paint","longtask"](mode=trace 时使用)
sessionNameNo浏览器会话名称,默认当前活跃会话(mode=check 时使用)
slowRequestMsNo慢请求阈值毫秒,默认 1000;可覆盖 budgets.slowRequestMs(mode=check 时使用)
enableScreenshotsNo是否在追踪期间定期截图,默认 false(mode=trace 时使用)
Behavior3/5

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

No annotations provided, so description carries full burden. It discloses that check collects and evaluates metrics, trace records full trace and outputs HAR and structured data. However, it does not mention side effects (e.g., page reload, permissions) or details about how the tool interacts with the browser state.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise with only two sentences. The first sentence gives the overall purpose and version note, the second explains the mode parameter. No extraneous information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 9 parameters, nested objects, and no output schema, the description covers the core functionality and mode differentiation. It is complete enough for an agent to understand the main use cases, though it could briefly mention what the output of each mode looks like (e.g., budget evaluation result, HAR file).

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3. The description adds context by explaining that the 'mode' parameter differentiates the two sub-modes, but otherwise the parameter descriptions in the schema are already detailed. The description does not add significant new meaning beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states it is a performance analysis tool with two distinct sub-modes (check/trace). It distinguishes itself by mentioning the merge of two previous tools (browser_performance_check/trace), helping differentiate from sibling tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explains the two modes and their purposes: check for collecting metrics against budget, trace for full traces. It provides explicit context for usage but does not mention when not to use this tool or alternative tools (e.g., browser_network).

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

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