Opik MCP Server

The official Model Context Protocol (MCP) server for Opik, the open-source LLM observability and evaluation platform, built by Comet. Plug your AI host (Claude Code, Cursor, VS Code Copilot, MCP Inspector) directly into your Opik workspace: read traces, log scores, save prompt versions, and ask Ollie, Opik's in-product AI assistant, investigative questions, all from the chat.

Built for LLM engineers who already run Opik and want to drive it from the same AI assistant they code with.

Migrating from the old npx opik-mcp? The TypeScript server is deprecated and sunsets on 2026-11-15. Swap npx -y opik-mcp for uvx opik-mcp@latest in your MCP client config. Full guide: legacy/typescript/MIGRATION.md.

You:    "Why did the experiment 'gpt-4o-rerank-v3' regress on factuality?"
Claude: → ask_ollie → reads experiment + traces → "Three traces failed because…"

You:    "Score trace 7f2e… 0.9 on helpfulness with reason 'great recovery'."
Claude: → write(score.create) → done

Install

opik-mcp is a Python package (requires Python 3.13+). The recommended way to run it is uvx, which fetches and runs the latest published version on demand — no global install, no virtualenv juggling.

Install uv once:

curl -LsSf https://astral.sh/uv/install.sh | sh   # macOS / Linux
# or: brew install uv

You'll need two things from your Opik workspace:

• OPIK_API_KEY — get it from comet.com/api/my/settings/.
• OPIK_WORKSPACE — your workspace name (lowercase, as it appears in the URL). E.g. https://www.comet.com/acme-ai/... → OPIK_WORKSPACE=acme-ai. COMET_WORKSPACE is accepted as a deprecated alias.

Cloud, with an API key: set it unless your account default is the one you want. Left out, the server sends default, which Comet resolves to your account's default workspace. That works, but if you actually work in a named workspace you will be pointed at a different one with nothing to tell you — your reads come back from the wrong place rather than failing.

Cloud, over OAuth: leave it unset. The workspace comes from the token you authorized, and the server ignores this setting entirely.

Local / open source: leave it unset. Open source Opik has a single workspace named default and no way to create others, which is exactly what the fallback gives you.

Self-hosted Comet: set it. Unlike open source, these deployments have real named workspaces, and the same silent-wrong-workspace risk applies.

Whichever applies, make sure the value is actually substituted. Snippets in the wild ship placeholders like <your-workspace> or ${input:OPIK_WORKSPACE}; pasted as-is, those are not workspace names. The server now refuses them outright rather than letting the backend answer with an auth error that explains nothing.

Claude Code

Add the server with one command:

claude mcp add --transport stdio opik-mcp \
  --env OPIK_API_KEY=<your-key> \
  --env OPIK_WORKSPACE=<your-workspace> \
  -- uvx opik-mcp

Or edit ~/.claude.json directly:

{
  "mcpServers": {
    "opik-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": ["opik-mcp"],
      "env": {
        "OPIK_API_KEY": "<your-key>",
        "OPIK_WORKSPACE": "<your-workspace>"
      }
    }
  }
}

Restart Claude Code. Verify with /mcp — opik-mcp should appear as connected. Then, in the chat, ask: "list my Opik projects" — Claude will call the list tool and you'll see your workspace's projects.

Cursor

Edit ~/.cursor/mcp.json (global) or .cursor/mcp.json (project), or open Cmd+Shift+J → Features → Model Context Protocol:

{
  "mcpServers": {
    "opik-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": ["opik-mcp"],
      "env": {
        "OPIK_API_KEY": "<your-key>",
        "OPIK_WORKSPACE": "<your-workspace>"
      }
    }
  }
}

Reload Cursor; the green dot next to opik-mcp in the MCP panel confirms the connection. Ask in chat: "list my Opik projects".

Cursor 60s timeout. Cursor enforces a hard tool-call timeout that doesn't reset on progress notifications. Long ask_ollie turns will fail on Cursor. See Known host limits.

VS Code Copilot

.vscode/mcp.json in your workspace (or User Settings JSON):

{
  "servers": {
    "opik-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": ["opik-mcp"],
      "env": {
        "OPIK_API_KEY": "<your-key>",
        "OPIK_WORKSPACE": "<your-workspace>"
      }
    }
  }
}

Reload the window; the Copilot Chat MCP indicator shows opik-mcp once the server is reachable. Ask in chat: "list my Opik projects".

MCP Inspector (manual testing)

OPIK_API_KEY=<your-key> OPIK_WORKSPACE=<your-workspace> \
  npx @modelcontextprotocol/inspector uvx opik-mcp

Self-hosted Opik

Add COMET_URL_OVERRIDE (and OPIK_URL if Opik lives at a non-default path) to the same env block in your host config:

{
  "mcpServers": {
    "opik-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": ["opik-mcp"],
      "env": {
        "OPIK_API_KEY": "<your-key>",
        "OPIK_WORKSPACE": "<your-workspace>",
        "COMET_URL_OVERRIDE": "https://opik.your-company.com",
        "OPIK_MCP_ANALYTICS_SOURCE": ""
      }
    }
  }
}

Omit OPIK_WORKSPACE on an open-source deployment, where default is the only workspace; keep it on a self-hosted Comet, which has real named ones.

ask_ollie and run_experiment are available on Comet Cloud only — on self-hosted those calls will fail at dispatch, so use read / list / write directly. Setting OPIK_MCP_ANALYTICS_SOURCE="" opts your install out of the cloud-Comet source label on telemetry events.

Tools

opik-mcp exposes a small, outcome-oriented surface — six tools that cover the full lifecycle (read → annotate → curate → author → iterate).

read

One tool for any "show me X" question. Takes an entity_type plus an id (UUID or, for nameable types, a name) or a full opik:// URI. Composite reads (trace, prompt) inline their children so a single call returns the full picture.

Supported entities: project, trace, span, test_suite, experiment, prompt. Name-based lookup is available for project, experiment, prompt, test_suite (slower — two API calls — and may return multiple matches).

read(entity_type="trace", id="7f2e3c8a-…")
read(entity_type="project", id="demo")          # name lookup
read(entity_type="trace", id="opik://traces/7f2e3c8a-…")

list

Browse a collection with optional name filter and pagination. Project-scoped types (trace, test_suite_item, prompt_version) require their parent UUID.

list(entity_type="experiment", page=1, size=25)
list(entity_type="experiment", name="rerank")          # name substring filter
list(entity_type="trace", project_id="<project-uuid>") # traces of one project

ask_ollie

For investigative questions, cross-entity synthesis, or anything that needs Opik domain expertise. Ollie has direct read access to your workspace and can execute writes (scores, comments, test-suite items, prompt versions) mid-stream when asked.

ask_ollie(query="Why are spans in project 'demo' slower this week than last?")
ask_ollie(query="Compare experiments A and B on factuality. Score the bottom 5 traces of A 0.2 with reason.")

Returns the assistant's final text plus a thread_id. Pass it back on follow-ups to preserve context — Ollie has no memory across threads.

YOLO mode (default). Writes Ollie performs mid-stream execute without a per-action confirmation. Each auto-approval is logged as a JSON audit row on the opik_mcp.audit Python logger. To require confirmation instead, set OPIK_MCP_AUTO_APPROVE=disabled — Ollie's confirm requests then surface as typed errors you can manually re-issue.

Available on Comet Cloud only.

write

Universal write dispatcher. Pass operation + data and the dispatcher validates the payload, applies the right REST verb, and returns the backend response.

Operations:

write(operation="score.create", data={
  "target": "trace",
  "target_id": "7f2e3c8a-…",
  "name": "helpfulness",
  "value": 0.9,
  "reason": "great recovery"
})