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VitexSoftware

mcp-server-webdriver

devtools_performance

Read-only

Retrieve browser Navigation Timing metrics to diagnose slow page loads, including TTFB, DOM content loaded, and full load time. Optionally get per-resource timing to pinpoint expensive assets.

Instructions

Return page performance timing from the browser Navigation Timing API.

navigation — key milestones for the current page load: ttfb_ms — Time to First Byte (server latency) dom_loaded_ms — DOMContentLoaded (page parsed, defer scripts done) load_ms — full load event (all resources fetched) dns_ms — DNS lookup duration connect_ms — TCP/TLS connection duration request_ms — time from request sent to last response byte transfer_size — response body size in bytes

resources (when include_resources=True) — per-asset breakdown: name, type, duration_ms, transfer_size, start_time

Use this to identify slow pages, expensive assets, or server latency. Complements devtools_network_all which captures requests via BiDi listeners.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
include_resourcesNoInclude per-resource timing entries (stylesheets, scripts, images…). Can be large on busy pages.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Behavior4/5

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

Annotations show readOnlyHint=true, and description adds context about reading timing data, and notes that include_resources parameter 'Can be large on busy pages', disclosing potential performance impact.

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?

Well-structured with bullet points, front-loaded purpose, no redundant sentences. Every sentence adds value.

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?

Description explains return structure in detail, complements output schema. For a tool with one parameter and clear annotations, this is complete.

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% with description for the boolean parameter. The description adds caution about size when true, providing value beyond 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?

Description specifies exact resource: 'page performance timing from the browser Navigation Timing API'. Lists fields and distinguishes from sibling 'devtools_network_all' which captures requests via BiDi listeners.

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?

States 'Use this to identify slow pages, expensive assets, or server latency' and mentions complementing devtools_network_all, providing clear context but no explicit when-not.

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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