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chrome_page_load_resource_hotspots

Read-onlyIdempotent

Rank URL-bearing resource slices by duration and overlap within a page load window to pinpoint slow requests for performance optimization.

Instructions

Rank URL-bearing Chrome resource/request slices in a page-load/raw window. Returns timing, overlap, process/thread/machine_id, URL. Use after chrome_page_load_resource_summary to drill into slow URL slices. Filters: page_load/window, min_dur_ms default 50, limit, max_string_len. slice_duration_status='incomplete_duration' means dur=-1; overlap is measured to window end or trace_end().

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNoOptional max rows to return. Defaults to 100 and is capped at 5000. Must be > 0 when set.
phaseNoOptional page-load phase window. If set without `page_load_id` or `navigation_id`, uses the latest page load in the trace. Values: navigation_to_fcp, navigation_to_load, dcl_to_fcp, fcp_to_load.
trace_idNoOptional trace id returned by `load_trace`. Omit to use the active trace.
end_ts_nsNoOptional raw trace timestamp upper bound in nanoseconds, exclusive. This uses the same unit as the returned `ts` column. ANDs with any page-load window.
min_dur_msNoOptional minimum resource-like slice duration in milliseconds. Defaults to 50 ms. Pass 0 to see all matching resource slices.
start_ts_nsNoOptional raw trace timestamp lower bound in nanoseconds. This uses the same unit as the returned `ts` column. ANDs with any page-load window.
page_load_idNoOptional page-load id used to scope resources to one navigation phase. Matches `chrome_page_loads.id`. Mutually exclusive with `navigation_id`. If set without `phase`, defaults to `navigation_to_fcp`.
navigation_idNoOptional Chrome navigation id used to scope resources to one navigation phase. Matches `chrome_page_loads.navigation_id`. Mutually exclusive with `page_load_id`. If set without `phase`, defaults to `navigation_to_fcp`.
max_string_lenNoOptional per-string-cell character cap applied to returned rows only. Unset preserves full strings for precision; accepts both numbers and numeric strings. Must be > 0 when set.

Tool Definition Quality

A4.2/5.0
Behavior4/5

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

Annotations already indicate the tool is read-only and idempotent. The description adds useful behavioral details about the slice_duration_status meaning and overlap measurement, complementing the annotations without contradiction.

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 three sentences, front-loaded with the core purpose, followed by usage guidance and a note on parameters and status. No wasted words, very efficient.

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?

The description covers purpose, return fields, usage context, key filters, and a behavioral nuance. Given no output schema, it provides enough context for the agent to understand the tool's role and basic output, though more explicit output structure could help.

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% with detailed parameter descriptions. The description summarizes key filters and defaults, adding high-level grouping but not significantly 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 the tool ranks URL-bearing resource slices in a page-load/raw window. It specifies the verb 'rank', the resource, and the context, and distinguishes from sister tool chrome_page_load_resource_summary by indicating it is used to drill into slow slices after that summary.

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 explicitly says to use the tool after chrome_page_load_resource_summary to drill into slow URL slices, providing clear sequencing. It also lists key filters, though it does not explicitly state when not to use it.

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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