Opik is an open-source platform for tracing, evaluating, and monitoring applications that use large language models, retrieval systems, or AI agents. Teams use it to inspect agent activity, manage prompts, run evaluations, and monitor these applications in production.
Borrowing it
Nothing to install: this file belongs to comet-ml/opik. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/comet-ml/opik/main/.agents/skills/writing-e2e-tests/SKILL.mdgit clone --depth 1 https://github.com/comet-ml/opikWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/comet-ml/opik/writing-e2e-tests)<a href="https://agentmods.dev/skills/comet-ml/opik/writing-e2e-tests"><img src="https://agentmods.dev/badge/skills/comet-ml/opik/writing-e2e-tests/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/comet-ml/opik/writing-e2e-tests"><img src="https://agentmods.dev/badge/skills/comet-ml/opik/writing-e2e-tests.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 5 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium MCP Rug Pull · line 120 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 123 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 132 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 135 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium Rogue Agent · line 143 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00126 | $0.02863 |
| Opus 5.5 | $0.00050 | $0.01145 |
| Sonnet 5.5 | $0.00025 | $0.00573 |
| Haiku 4.5 | $0.00013 | $0.00286 |
Grade A, and why
writing-e2e-tests scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 175 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing E2E Tests
This skill is how we add an end-to-end test to the Opik E2E suite. You give it a feature, page, or branch; it runs a proven loop end-to-end and leaves you with a working, locally-verified Playwright test.
Announce at start: "I'm using the writing-e2e-tests skill to add an E2E test for X."
Where tests live
The suite is at tests_end_to_end/e2e/. Inside it:
- Specs:
tests/<feature>/<name>.spec.ts— one feature directory per page family (datasets,trace-explore,experiments,test-suites,online-evaluation, …). - Page Object Models:
pom/<name>.page.ts— one class per page, methods for the interactions a test needs. - Fixtures:
fixtures/<name>.fixture.ts— seed entities (project, dataset, trace, experiment, testSuite) and tear them down. Composed in a chain; re-exported fromfixtures/index.ts. - SDK clients:
core/sdk/—sdkClient.python(HTTP wrapper over the bridge) andsdkClient.typescript(directnew Opik({...})) for seeding.core/backend/holds the typed REST client for inspection + teardown. - Bridge:
services/opik-sdk-driver/— a FastAPI app (run withuv) wrapping the Python SDK, exposing routes the TS clients call. Playwright'swebServerdirective auto-spawns it during a test run; you don't start it by hand.
Specs and POMs import through path aliases: import { test, expect } from '@e2e/fixtures' and import { LogsPage } from '@e2e/pom/logs.page'.
Tooling — already set up
- The
PlaywrightMCP (live-UI exploration) and theplaywright-testMCP (browser_generate_locator) are already configured in the repo's.mcp.json. No setup step. - Tests run via the plain Playwright CLI from
tests_end_to_end/e2e/. ThewebServerdirective spawns the bridge automatically.
Conventions
Read conventions.md before writing any POM or spec. It carries the rules that keep tests legible and stable: mandatory test.step() wrapping, UI-first assertions, selector preference, public-SDK-only seeding, fixture seed shapes, and the tag taxonomy. They aren't optional polish — each prevents a class of failure.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2mo ago First seen · 175 lines · 126 tokens per session scan A 281cba0ff01f
writing-e2e-tests is a skill published in the GitHub repository comet-ml/opik (22,998 stars, last pushed today), licensed Apache-2.0. It adds 126 tokens to every session and 2,863 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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