Skip to main content
Glama
vola-trebla

playwright-trace-decoder-mcp

by vola-trebla

Server Configuration

Describes the environment variables required to run the server.

NameRequiredDescriptionDefault

No arguments

Instructions

Guidance the server publishes about itself, which clients place ahead of the tool catalog so the model reads it before choosing anything.

This server publishes no instructions, or was last inspected before Glama recorded them.

Capabilities

Features and capabilities supported by this server

Protocol revision2025-11-25

CapabilityDetails
tools
{
  "listChanged": true
}

Tools

Functions exposed to the LLM to take actions

NameDescription
get_test_metadataA

Returns test metadata: title, browser, platform, viewport, and start time

get_trace_summaryB

Returns the failing action and top-level error message from a Playwright trace

get_action_timelineA

Returns a paginated timeline of all actions with locators and timings. Use limit/offset to page through large traces.

get_filtered_network_logsA

Returns only 4xx/5xx network responses, stripping static assets. Use limit/offset to page through results.

get_console_errorsB

Returns JS exceptions and warnings. Use limit/offset to page through results.

get_aria_accessibility_treeA

Returns the ARIA accessibility tree (YAML) for a frame snapshot in the trace. Reduces DOM token cost by ~90% vs raw HTML. Use action_index to target a specific action — defaults to the failed action, or the last snapshot if no failure.

get_element_state_at_failureB

Returns DOM attributes of the failing element at the moment of failure

analyze_race_conditionsA

Detects potential race conditions by finding network requests that were still in-flight when a user interaction action fired. Returns flagged actions with pending requests.

get_dom_mutation_deltaA

Diffs the ARIA tree before and after a specific action. Returns added and removed elements so the agent sees exactly what changed without comparing two full DOM dumps.

get_causal_chain_for_failureA

Walks backwards from the failed action and builds a chronological chain of preceding actions, network errors, and console errors. Surfaces the most likely root cause.

generate_error_signatureA

Generates a stable 12-char hash signature for a test failure by normalizing the error message (stripping paths, numbers, UUIDs). Use to group duplicate failures across parallel CI runs without reading each trace manually.

compare_tracesA

Compares a passing and a failing trace of the same test. Aligns actions by sequence, finds the first timing or structural divergence, and summarises network differences. Use to diagnose flakiness — what was different in the run that failed.

get_screenshot_at_failureA

Returns the screenshot (base64 JPEG) from the trace closest to the moment of failure. Use when get_aria_accessibility_tree returns an empty or unhelpful tree — the image shows exactly what was on screen. Pass screenshot_index to retrieve any specific screenshot from the trace (0-based); omit to get the one nearest to the failure.

correlate_dom_and_networkA

Joins the HAR network log and DOM snapshots into an explicit causal chain. For each action where a network response completed and the DOM mutated within ±100ms, returns the triggering request URL, response status, body snippet, and the exact DOM nodes that appeared or disappeared. Background polling and analytics pixels are filtered out. Use to diagnose race conditions and async rendering bugs — removes hallucination from the question 'did this fetch cause this DOM change?'

extract_trace_metadata_strictA

Strictly inspects a Playwright trace archive and returns format version, retry session breakdown, and HAR payload mode. Handles .pwtrace.zip extensions (newer Playwright CI), multi-retry archives (identifies which retry failed), and all three HAR modes: embed (bodies inline), attach (bodies as separate files), omit (headers only). Use before other trace tools when the archive may be from an unfamiliar Playwright version or CI configuration — confirms the trace is valid and tells you what data is available.

detect_performance_anomaliesA

Detects Long Tasks and frame drops that cause Playwright timeouts. Analyses screencast-frame timestamps for main-thread blocking (gaps > 50ms), flags actions that took longer than 500ms, counts concurrent in-flight network requests during each slow action, and checks for monotonically increasing action durations (suspected memory leak). Returns a ranked list of anomalies with a suspected_cause so the agent can distinguish a blocked main thread from network saturation or a navigation timeout — without blaming a missing element.

map_locator_to_sourceA

Maps a failing browser interaction (or a specific action index) to its corresponding line of code in the test file using the execution stack from the test runner.

extract_critical_framesA

Extracts key screencast screenshots (base64 JPEG) from a temporal window around a test failure or the end of the trace, resolved with their associated test step titles.

trim_trace_archiveA

Shrinks a Playwright trace zip file by deleting screenshots outside the critical failure window (t_fail - 5s to t_fail + 1s). Returns original vs trimmed size and path to the new archive (.trimmed.zip).

Prompts

Interactive templates invoked by user choice

NameDescription

No prompts

Resources

Contextual data attached and managed by the client

NameDescription

No resources

Latest Blog Posts

MCP directory API

We provide all the information about MCP servers via our MCP API.

curl -X GET 'https://glama.ai/api/mcp/v1/servers/vola-trebla/playwright-trace-decoder-mcp'

If you have feedback or need assistance with the MCP directory API, please join our Discord server