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Core Web Vitals

web_vitals
Read-onlyIdempotent

Core Web Vitals from real Chrome users. Pick with mode: now = The latest field data for a page or site. Needs url. trend = Weekly history, before and after a change date. Needs url.

Input Schema

NameRequiredDescriptionDefault
urlNoFull address of the page, for example https://example.com/pricing.
modeNoDefault now.
detailNobrief = short summary.
memory_keyNosite_memory key, records this call.
change_dateNoOptional date a speed fix went live, YYYY-MM-DD.

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • removedOutput schema / description
      Removed value: -"The result as structured data; fields depend on mode."
  2. Changed2 schema fields changed
    • changedInput schema / properties / detail / description
      Previous value: -"brief returns a short summary, default full."New value: +"brief = short summary."
    • changedInput schema / properties / memory_key / description
      Previous value: -"Optional site_memory key, to record this call in the site memory."New value: +"site_memory key, records this call."
  3. Changed1 schema field changed
    • addedInput schema / properties / detail
      Added value: +{
+  "description": "brief returns a short summary, default full.",
+  "enum": [
+    "full",
+    "brief"
+  ],
+  "type": "string"
+}
  4. Changed1 schema field changed
    • addedInput schema / properties / memory_key
      Added value: +{
+  "description": "Optional site_memory key, to record this call in the site memory.",
+  "maxLength": 80,
+  "type": "string"
+}
  5. Added

TDQS

A4.1/5.0
Behavior4/5

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

Annotations already establish read-only, idempotent, non-destructive, open-world semantics, and the description adds real value on top: the data source is real Chrome user field data, and trend returns weekly history segmented before/after a change date. It does not mention quotas, latency, or auth, which is a minor gap given the annotation coverage.

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?

Three tight sentences that front-load the resource, then the mode decision rule; no filler or repetition of the title. Every clause carries either scope or a selection condition.

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 a full schema, an output schema covering return values, and annotations covering the safety profile, the description supplies the missing decision logic (which mode, what each needs). It stops short of clarifying optionality of change_date within trend or what 'brief' detail omits, but nothing critical for correct invocation is absent.

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 coverage is 100%, so the baseline is 3, but the description genuinely enhances the mode enum by explaining what each value returns, and ties url/change_date to the mode that requires them. It leaves detail and memory_key to the schema.

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

Purpose4/5

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

Names a specific resource — Core Web Vitals field data from real Chrome users — and splits it into two clearly labeled modes (now = latest field data, trend = weekly history). An agent can tell what it returns, though there is no explicit differentiation from nearby siblings like measure or technical.

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?

'Pick with mode: now = ... trend = ...' gives a direct selection rule for the two modes, and each mode states its prerequisite ('Needs url'). No alternative-tool routing or exclusion guidance against the other 30+ siblings is offered, which keeps it short of a 5.

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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