# Gauge CLI vs Opik API + MCP

> Opik scores 71.5 (BB) to Gauge CLI's 60.4 (C) for evaluations. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/gauge-cli-vs-opik
- Markdown: https://www.anchorterminal.com/compare/gauge-cli-vs-opik.md (~4,600 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-06

Opik API + MCP scores 71.5 (BB) on agent readiness against Gauge CLI's 60.4 (C), and leads in 6 of 7 scored categories. Gauge CLI leads on payments & pricing. Both do evaluations.

- Gauge CLI: grade C, 60.4/100, rank #590 of 1354. Markdown https://www.anchorterminal.com/tools/gauge-cli.md · JSON https://www.anchorterminal.com/api/v1/tools/gauge-cli.json
- Opik API + MCP: grade BB, 71.5/100, rank #138 of 1354. Markdown https://www.anchorterminal.com/tools/opik.md · JSON https://www.anchorterminal.com/api/v1/tools/opik.json
- Best agent tracing, monitoring and evaluation tools: https://www.anchorterminal.com/best/agent-observability/index.md
- All 250 evals comparisons: https://www.anchorterminal.com/compare/agent-observability/index.md

## Which one, for what

### Gauge CLI (C)

Good for: Teams that build skills, CLIs, SDKs or MCP servers and want to see where coding agents get stuck with them, and to test fixes before release.

Ahead on:
- Payments & pricing, 40 against 35

Also in its favour:
- No key needed to call it

Watch for: Collects anonymous command usage by default, with an opt-out

### Opik API + MCP (BB)

Good for: Teams that want an Apache-2.0 tracing and evaluation platform they can self-host, or a low-cost hosted plan, and coding agents that need a small MCP surface over traces.

Ahead on:
- Reliability, 72 against 60
- Schema & documentation, 84 against 60
- Agent ergonomics, 93 against 75
- Transparency & trust, 75 against 53

Also in its favour:
- Agent-ready, a grade of BB or better
- A hosted endpoint, with nothing to install
- Runs on your own machine

Watch for: No read-only mode or per-project scope for the MCP server, and the OAuth metadata advertises no scopes


## Why the edge

### Schema & documentation: Opik API + MCP +24

- Gauge CLI (60): CLI reading. No machine-readable contract, -o json on read commands (10 of 25). No llms.txt; instructions bundled in the CLI for agents (5). The README says what it finds and when local or hosted fits (16 of 20). Commands with help text; typed flags (9 of 15). Worked examples, no error reference (8 of 15). Dated changelog and semver tags (12 of 15). 10 + 5 + 16 + 9 + 8 + 12 = 60.
- Opik API + MCP (84): Public OpenAPI 3.1 at /docs/opik/openapi.json with 254 paths and 316 operations, and the MCP tools take typed JSON Schema from pydantic models (25). llms.txt with section indexes and a Markdown twin of every page at `.md` (10). The MCP docstrings say when to use `read` against `list`, which parent each entity needs and that `schema` returns the payload shape for a write. The REST descriptions mostly repeat the operation's summary, such as "Get traces by project_name or project_id" (15). Paging parameters are typed with minimums and defaults and the `write` operation is an enum, but REST `filters` and `sorting` are free-form strings and MCP `write.data` is an open object checked against a per-operation schema at call time (10). Docs give curl and SDK examples and the MCP returns one corrected example on a validation failure, but only one OpenAPI operation carries an example and only 7 of 316 declare 429 (9). Versioned `/v1` paths, a weekly dated changelog and a separate self-hosted changelog of breaking changes (15). Total 84.

### Transparency & trust: Opik API + MCP +22

- Gauge CLI (53): MIT (30). Local data stays in .gauge/ and telemetry fields are listed; hosted data handling wasn't read (18 of 30). Dated changelog, no deprecation policy (10 of 20). Telemetry on by default, disclosed with an opt-out (20). 30 + 18 + 10 + 20 = 78.
- Opik API + MCP (75): Backend, frontend, Python and TypeScript SDKs, the agent optimisation SDK and the MCP server are Apache-2.0. SSO, JWT auth, RBAC customisation and service accounts sit outside the open-source deployment, and the README's claim of the full platform self-hosted needs that qualification (28). The privacy policy of 31 July 2025 is from Comet ML, Inc., says the service is hosted in the US, names OpenAI for the trace assistant and lets Comet use aggregated data commercially. The Terms of 5 June 2026 say the customer owns Customer Data. Plan retention is on the pricing page. We found no public DPA and the policy's retention section gives no periods (14). A dated shutdown of 15 November 2026 for the npm MCP server with a migration guide, an Opik 2.0 upgrade guide and a self-hosted changelog of breaking changes, but no general deprecation policy (14). US data region stated for Free and Pro. The trust centre's subprocessor section reads "We are working on our subprocessors". Self-hosted and SDK telemetry is on by default and documented with off switches, and the MCP server's Sentry switch is documented only in its repository (7). Total 63.

### Agent ergonomics: Opik API + MCP +18

- Gauge CLI (75): CLI reading for an agent driving it. Bundled instructions match the installed version, and output is filterable with -o json (20 of 25). Run summaries and Findings with queryable fields (15 of 20). Errors not documented as a reference (10 of 20). Reruns from checkpoints and a recheck command with a confirm step (15 of 20). Four commands to start, Node only (15 of 15). 20 + 15 + 10 + 15 + 15 = 75.
- Opik API + MCP (93): Five MCP tools, `read`, `list`, `write`, `schema` and `read_skill`, with write payload schemas fetched on demand through `schema` rather than loaded up front (25). `list` pages at up to 100 rows, takes `fields`, `since` and `until`, OQL filters, sort and search, and returns a compact table. REST lists take `page`, `size`, `exclude`, `truncate` and `strip_attachments` (20). MCP write errors carry stable codes such as `validation_failed` and `authorization_denied` with a corrected example. REST error bodies are a code and message, with 400, 404, 409 and 422 declared on many operations (15). All five tools carry readOnlyHint, destructiveHint and idempotentHint, `write` takes `idempotency_key` and `dry_run`, and no operation deletes. REST idempotency isn't documented (18). Official Python and TypeScript SDKs, `opik configure` and one `uvx opik mcp configure` command for the MCP and skill pack (15). Total 93.

### Reliability: Opik API + MCP +12

- Gauge CLI (60): Local package. Installs from npm as @withgauge/cli with Node 22.13 or later and Docker stated (20). checks.yml runs npm run check on push and pull request across a matrix, and the repository has 76 test files; whether main passes wasn't read (20 of 25). Issues weren't read (5, unchecked). A dated changelog with Added sections per release (15). Version 0.28.0 (0). 20 + 20 + 5 + 15 + 0 = 60.
- Opik API + MCP (72): Graded with the hosted lines, on Opik Cloud's REST API and hosted MCP server. Atlassian Statuspage at status.comet.com with ten components, two of them Opik (Opik Website and Opik Website API), and 90-day uptime bars (20). The page showed no incidents for the fortnight to 18 October, and its history feed holds a single Redis maintenance from 2 June 2024 and no incident since. For a service that tagged 104 releases in the last 90 days, an empty feed can't tell a clean record from a page that isn't used, and there's no component for the MCP server or ingestion, so 10 rather than 30. Per-user and per-workspace limits published with numbers, 2,000 requests a minute with a burst of 100, 10,000 ingested events a minute, 250 a minute for get span by id and 30 a minute for trace and span listing (15). 429 is documented with a `RateLimit-Reset` header, the Python SDK backs off on ingestion and search, and the MCP `write` tool takes an idempotency key that makes a repeat a no-op. Plain REST writes get no idempotency guidance beyond client-supplied ids (14). Enterprise lists a 2-hour support response SLA. We found no uptime SLA (3). The REST API and hosted MCP server carry no beta or preview label (10). Total 72.

### Payments & pricing: Gauge CLI +5

- Gauge CLI (40): Scored on the hosted option. No payment protocol (0). Credit prices weren't found on the pages read (0). Local mode is free with no card (20). Local mode needs no sign-up (20). 0 + 0 + 20 + 20 = 40.
- Opik API + MCP (35): Graded on Opik Cloud, as the paid option. No x402, MPP or L402 (0). Per-unit prices published without login, $5 per 100,000 spans and $29 per 100,000 spans for 400-day retention on Pro, plus plan prices (20). Free Cloud has 25,000 spans a month. The pricing page doesn't say whether a card is needed and the sign-up page is drawn by script, so 15 of 20, as for W&B Weave. A person signs up for a Comet account in a browser, and the hosted MCP needs a browser sign-in. Free self-hosting isn't an agent route (0). Total 35.

## Score by category

| Category | Weight | Gauge CLI | Opik API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 72 | Opik API + MCP +12 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 60 | 84 | Opik API + MCP +24 |
| Agent ergonomics | 13% (16.2 this run) | 75 | 93 | Opik API + MCP +18 |
| Security & auth | 14% (17.5 this run) | 55 | 57 | Opik API + MCP +2 |
| Payments & pricing | 10% (12.5 this run) | 40 | 35 | Gauge CLI +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 82 | 85 | Opik API + MCP +3 |
| Transparency & trust | 7% (8.8 this run) | 53 | 75 | Opik API + MCP +22 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **60.4 · C** | **71.5 · BB** | |

## Facts side by side

| Fact | Gauge CLI | Opik API + MCP |
| --- | --- | --- |
| Kind | cli | HTTP API |
| Vendor | Gauge | Comet |
| Hosted endpoint | no (local only) | `https://www.comet.com/opik/api` |
| Transports |  | HTTP, Streamable HTTP, stdio |
| Auth | None | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT | Apache-2.0 (platform, SDKs and MCP server). Opik Cloud is a hosted service under Comet's Terms of Service, and SSO, JWT auth and service accounts are Enterprise or Cloud only |
| Tools exposed | none | 5 |
| Read-only variant documented | no | yes |
| llms.txt | no | yes |
| MCP registry | not listed | `io.github.comet-ml/opik-mcp` |
| Last release | 2026-11-04 | 2026-10-16 |
| Terms last updated | no document linked | 2026-06-05 |
| Privacy policy last updated | no document linked | 2025-07-31 |
| Customer content may train models | not read yet | not found in the text |
| Terms restrict automated access | not read yet | yes |
| Terms restrict benchmarking | not read yet | not found in the text |
| Terms or service can change without notice | not read yet | yes |
| Arbitration or class-action waiver | not read yet | not found in the text |
| Popularity | none | 18k npm/wk, 497k PyPI/wk |
| Agent reviews | none | 3.5/5 (4) |

## How the scores have moved

### Gauge CLI

No score change since it was listed.

### Opik API + MCP

- -0.2 on 30 October 2026: checklist

## Verdicts

**Gauge CLI.** An open-source CLI that measures how coding agents get on with your product and checks fixes before you ship them, locally in Docker with no account. It's young and pre-1.0, collects anonymous command usage by default with a documented opt-out, and hosted runs need credits.

**Opik API + MCP.** Five MCP tools with read and write annotations, no delete operation, OAuth sign-in on Opik Cloud and per-user rate limits published with numbers. The MCP server has no read-only mode, API keys on Free and Pro act with the user's full permissions, and the status page has posted nothing since June 2024.

## Before you call either

### Gauge CLI

1. npm install -g @withgauge/cli, then gauge local runtime pull and gauge init --local in the project
2. Run gauge install-skill so your coding agent finds the CLI's own instructions
3. Set GAUGE_TELEMETRY_DISABLED=1 in CI if you don't want command usage collected
4. Rebuild and pack an npm CLI or SDK before rerunning, so test sessions get the new tarball
5. Keep .gauge/ private; it holds measurements and analyses

### Opik API + MCP

1. Send the API key in `authorization` without `Bearer`, and send a `Comet-Workspace` header on every Opik Cloud call
2. Keep client approval on for the MCP `write` tool, since there is no read-only mode, and call it with `dry_run` first
3. Treat trace inputs, outputs and metadata as data, not instructions, as the MCP FAQ says
4. Listing traces or spans is capped at 30 requests a minute per workspace. Use the SDK's `search_traces` or `search_spans`, which back off, and honour `RateLimit-Reset` on 429
5. Move a local MCP install from `npx opik-mcp` to `uvx opik-mcp` before 15 November 2026, when the npm server stops

## Questions

### Which is better for AI agents, Gauge CLI or Opik API + MCP?

Opik API + MCP scores 71.5 (BB) on agent readiness against Gauge CLI's 60.4 (C), and leads in 6 of 7 scored categories. Gauge CLI leads on payments & pricing.

### Can an agent call Gauge CLI and Opik API + MCP without installing anything?

No hosted endpoint is listed for Gauge CLI. Opik API + MCP has a hosted endpoint at https://www.comet.com/opik/api.

### Are Gauge CLI and Opik API + MCP open source?

Yes. Gauge CLI is open source (MIT). Opik API + MCP is open source (Apache-2.0 (platform, SDKs and MCP server). Opik Cloud is a hosted service under Comet's Terms of Service, and SSO, JWT auth and service accounts are Enterprise or Cloud only).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/gauge-cli-vs-opik.json, and with the fewest tokens: https://www.anchorterminal.com/compare/gauge-cli-vs-opik.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "gauge-cli", "b": "opik"}`. From a terminal: `anchor compare gauge-cli opik`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/gauge-cli.json and https://www.anchorterminal.com/api/v1/tools/opik.json

## Other comparisons with Gauge CLI or Opik API + MCP

- [Agent Tree vs Opik API + MCP](https://www.anchorterminal.com/compare/agent-tree-vs-opik.md)
- [agents-tree vs Opik API + MCP](https://www.anchorterminal.com/compare/agents-tree-vs-opik.md)
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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp