analyze_operators
Analyze RxJS code for creation functions, operators, performance patterns, and best practices
LABSCO SUMMARY
Answers what the stream actually emitted instead of what the operators should do.
Reasoning about switchMap against mergeMap on paper is where RxJS bugs come from; running the snippet and reading the emissions with their timestamps settles it in one call. Pair that with the leak check, which is built around recognising the current cleanup idioms so it does not cry wolf on correct Angular or React code. The marble diagram is the part to hand to another person — it turns a timing argument into something you can look at.
What it is
A workbench for RxJS streams. Code is executed in an isolated worker and the emissions come back with timings, while the other tools read the same code statically for operator choices, subscription handling and lint rules.
What you get
- RxJS code run in a separate worker thread, returning what the stream emitted, when, and what it cost — with a timeout, an emission cap, and optional timeline and memory capture
- ASCII marble diagrams generated from timed events, with scale, duration and value display under your control
- Operator chain analysis over creation functions and operators, flagging performance patterns and offering alternatives
- Memory-leak detection that understands the modern cleanup patterns — takeUntilDestroyed, the async pipe, useEffect cleanup, onUnmounted — so idiomatic code is not reported as a leak
- Production patterns for the recurring problems: HTTP retry, debounced typeahead, polling with backoff, reconnecting WebSocket, form validation, state store, cache refresh
- Linting based on the eslint-plugin-rxjs-x rules with no ESLint runtime needed — recommended covers the common issues, strict adds the style rules, and the framework setting turns on Angular, React or Vue specific checks
Requirements
Nothing to authorize; it runs over stdio as npx @shuji-bonji/rxjs-mcp, or installed globally. Execution happens locally in a worker thread on your machine, bounded by the timeout and emission count you pass. The execute call takes either an expression that evaluates to an Observable or a snippet ending in one — an explicit return always works. The lint tool is regex-based best-effort analysis rather than a real ESLint run. It is a community project, not affiliated with the RxJS team. MIT.
Setup effort
One command — npx @shuji-bonji/rxjs-mcp
USE CASES
01
Settling what an operator chain really does
Run the snippet in isolation and read the emissions with their timings, capped at a number of values so an infinite stream still returns.
02
Explaining stream timing to someone else
Turn the timed events into an ASCII marble diagram, with the scale and duration set so the interesting part is visible.
03
Checking a subscription will actually be cleaned up
Analyse the code for missing teardown and uncompleted subjects, with the component lifecycle taken into account so idiomatic cleanup is not flagged.
04
Reviewing an RxJS change before merging it
Lint against the recommended or strict rule set for the framework in question, and read the operator analysis for the chains it flags.
05
Writing a resilient stream from scratch
Ask for the pattern for the use case — retrying HTTP, debounced search, polling with backoff, reconnecting sockets — in the framework you are working in.
6 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
detect_memory_leak
Analyze RxJS code for potential memory leaks and subscription management issues. Recognizes modern auto-cleanup patterns (takeUntilDestroyed, async pipe, useEffect cleanup, onUnmounted) to avoid false positives.
execute_stream
Execute RxJS code in an isolated environment and capture the stream emissions, timeline, and performance metrics. Code runs in a separate worker thread for security.
generate_marble
Generate ASCII marble diagrams to visualize RxJS stream emissions over time
lint_rxjs
Lint RxJS code snippets for common issues and best practices (regex-based best-effort analysis, no ESLint runtime required). Based on eslint-plugin-rxjs-x rules. Checks for nested subscribes, memory leaks, deprecated patterns, and more. Rules marked as type-info-required use heuristics and may have false positives/negatives. Supports framework-specific rules for Angular, React, and Vue.
suggest_pattern
Suggest RxJS patterns and best practices for common use cases
BEFORE YOU INSTALL
What to know first
Tools you get
6 tools when we connected.
Requires
npx on PATH
Where it runs
All 3 documented clients run the server on your machine.
CONTEXT COST
Light Standing cost
Rated by the size of the 6 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Server setup
TERMINAL
npx @shuji-bonji/rxjs-mcpMCP Clients
Claude Desktop, Cursor
JSON
{
"mcpServers": {
"rxjs": {
"command": "npx",
"args": [
"@shuji-bonji/rxjs-mcp"
]
}
}
}VS Code
VS CODE · JSON
{
"servers": {
"rxjs": {
"command": "npx",
"args": [
"@shuji-bonji/rxjs-mcp"
]
}
}
}
