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slice_descendants_breakdown

Read-onlyIdempotent

Drill into long tasks by expanding descendant slices under root slice IDs, aggregated by depth and name with bounded breakdown. Avoid manual recursive queries.

Instructions

Recursive child-slice expansion under known slice.id roots, aggregated as a bounded breakdown per (depth, name) group. Use to drill into a long task — after chrome_main_thread_hotspots or execute_sql returns a slice id — without hand-writing WITH RECURSIVE CTEs over slice.parent_id. Required: slice_ids. Optional bounds: min_dur_ms, max_depth, limit, include_args, max_string_len. The response echoes summary_scope, applied_filters, and missing_root_ids (missing root slice ids). Returned columns: root_id, depth, name, slice_count, inclusive_total_ms (do not sum across depths), self_ms (direct-child time subtracted, clamped at zero), max_ms, first_ts_ns (raw nanoseconds, not ms), example_slice_id (longest-duration descendant per group), and optionally example_args. incomplete_descendant_count counts dur<0 descendants excluded from duration aggregates.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
include_argsNoInclude an example args summary for one representative slice per group.
limitNoOptional max rows to return. Defaults to 100 and is capped at 5000. Accepts both numbers and numeric strings.
max_depthNoOptional maximum descendant depth. Defaults to 8. Must be > 0 when set; accepts both numbers and numeric strings.
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.
min_dur_msNoOptional descendant minimum duration in milliseconds. Defaults to 1 ms. Must be finite and non-negative; accepts both numbers and numeric strings.
slice_idsYesRoot slice ids to expand. The root slices themselves are omitted from the summary; returned rows aggregate matching descendants under each root. Accepts numbers or numeric strings.
Behavior4/5

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

Annotations already indicate read-only, non-destructive, idempotent behavior. Description adds details about response fields (summary_scope, applied_filters, missing_root_ids, incomplete_descendant_count) and column semantics, surpassing annotation coverage. No contradictions.

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

Conciseness4/5

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

Two concise sentences followed by a structured column list. Front-loads core purpose. The column list is necessary due to no output schema but is dense; slight room for streamlining.

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

Completeness5/5

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

With 6 parameters and no output schema, the description covers all essential aspects: purpose, usage scenario, parameter roles, return columns, and behavioral notes (e.g., incomplete descendants). It fully equips an agent to select and invoke the tool correctly.

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

Parameters4/5

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

Schema covers 100% of parameters. Description adds contextual meaning by explaining that root slices are omitted, output includes scope and filters, and column behavior like 'incomplete_descendant_count'. This enriches understanding beyond schema alone.

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?

Description explicitly states the tool performs recursive child-slice expansion under known slice IDs, aggregated per depth and name. It distinguishes from siblings by noting it saves hand-writing recursive CTEs, a unique capability among the listed 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?

Clearly advises using this tool after chrome_main_thread_hotspots or execute_sql returns a slice ID, providing explicit context. Lacks 'when not to use' but the use case is well-defined.

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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