Quattr

cwv_breakdown

Read-only

How do Core Web Vitals break down by rank bucket, device, or content category? Groups ONE vital — LCP seconds by default, or the 0–1 Lighthouse performance score, CLS, or INP via the vital parameter — using the SAME governed grouping and weighted rollup as QWA's Growth Trends drill-down, and joins organic clicks per group. Use for "LCP by rank bucket", "performance score by device", "CWV grouped by category". NOT a per-page table (use page_traffic_cwv), not a time series, not causal.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "date_range": "<date_range>",
      "group_by": "<group_by>"
    },
    "name": "cwv_breakdown"
  }
}

Input Schema

Name	Required	Description	Default
`top_n`	No	Maximum groups to return (rank_bucket/device have few; category can have many). Groups are ordered canonically for rank buckets, by clicks otherwise.
`vital`	No	Which Core Web Vital to aggregate per group: lcp (default, seconds), performance (0–1 Lighthouse score), cls (unitless), or inp (seconds).	lcp
`source`	No	Where Google search performance data is read from. Use "bigquery" ONLY when the user explicitly asks for BigQuery as the source AND describe_data_sources reports it available from live customer configuration — it returns far more granular per-query data (privacy-suppressed impressions appear under "[anonymized by google]").	default
`group_by`	Yes	What to group the vital by: rank_bucket (QWA's "Ranking 1 to 3" … "Ranking 40+" bands), device, or category (content category).
`date_range`	Yes	Explicit date range, e.g. "2026-05-01 to 2026-05-31". Both endpoints are INCLUSIVE — the END day is covered (a 7-day range = 7 days). Quattr weeks run Sunday–Saturday; for "last week" use the most recent complete Sun–Sat span.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 19, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare the read-only, non-destructive, closed-world profile, so safety is covered. The description adds real behavioral context beyond that: the vital is grouped with the same governed weighting/rollup as the Growth Trends drill-down, only ONE vital is aggregated, and clicks are joined per group. It stops short of return format or freshness details.

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?

Purpose is front-loaded, then scope, then exclusions — a sensible order. The opening rhetorical question slightly duplicates the sentence that follows it, which is the only real redundancy in an otherwise dense, information-carrying description.

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 no output schema, the description still conveys grouping dimensions, single-vital aggregation, the clicks join, defaults, and boundaries. It omits the exact return shape, but for a grouped-aggregate tool the usage and scoping information an agent needs is substantially covered.

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 the schema fully documents all five parameters including defaults and enum values. The description largely restates the vital default and value units already in the schema, adding only the "groups ONE vital" constraint. Baseline 3 is appropriate when the schema carries the parameter load.

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?

States a specific verb (breakdown/group) and resource (Core Web Vitals by rank bucket, device, or category), plus the join of organic clicks per group. It explicitly distinguishes itself from page_traffic_cwv and from time series, so an agent can route correctly without opening the schema.

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?

Gives concrete trigger phrases ("LCP by rank bucket", "performance score by device", "CWV grouped by category") and explicit exclusions with the alternative named ("NOT a per-page table (use page_traffic_cwv), not a time series"). When-to-use, when-not, and the alternative are all present.

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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