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slice_descendants_breakdown

Read-onlyIdempotent

Recursively expand and aggregate descendant slices under given root slice IDs, grouped by depth and name with count, total, and max duration. Ideal for drilling into long tasks after identifying a slice ID.

Instructions

Recursive child-slice expansion under known slice.id roots, aggregated as a bounded breakdown (slice_count / total_ms / max_ms 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 (root slice ids not present in the loaded trace — usually stale ids). Returned columns: root_id, depth, name, slice_count, total_ms, max_ms, first_ts_ns (raw nanoseconds, not ms), example_slice_id (longest-duration descendant per group), and optionally example_args.

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.
Behavior5/5

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

Annotations declare read-only, non-destructive, idempotent behavior, which the description reinforces. The description goes beyond annotations by detailing the response structure: echoes of summary_scope, applied_filters, missing_root_ids, and specific columns. 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?

The description is a single dense paragraph that front-loads the core purpose. Every sentence is informative, but the structure could be slightly improved with bullet points or breaking into logical sections. Nonetheless, it is concise and efficient.

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?

Despite lacking an output schema, the description fully explains the returned columns. All 6 parameters are described in the schema, and the description adds context for usage and output behavior. The tool's complexity (recursive expansion with aggregation) is well-covered, making it complete for an AI agent.

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

Parameters5/5

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

The input schema has 100% description coverage, but the description adds value by grouping parameters (Required: slice_ids, Optional bounds: ...), explaining defaults (e.g., 'Defaults to 100 and is capped at 5000' for limit), and clarifying that root slices are omitted. This contextual information enhances understanding 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 starts with a clear verb-resource-aggregation statement: 'Recursive child-slice expansion under known slice.id roots, aggregated as a bounded breakdown (slice_count / total_ms / max_ms per (depth, name) group).' It also differentiates from siblings like execute_sql by noting it avoids hand-writing recursive CTEs.

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

Usage Guidelines5/5

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

Explicitly states when to use: 'drill into a long task — after chrome_main_thread_hotspots or execute_sql returns a slice id.' It also explains the benefit: 'without hand-writing WITH RECURSIVE CTEs.' The required and optional parameters are listed, providing context for usage.

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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