# Arize Phoenix vs Galileo API + MCP

> Arize Phoenix has a score of 75.6 (BB) against Galileo API + MCP's 48 (D). Both do obs traces. The largest gap is reliability, 59 points. Category scores, facts, verdicts and agent notes side by side.

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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-05

Arize Phoenix has a score of 75.6 (BB) against Galileo API + MCP's 48 (D). Both do obs traces. The largest gap is reliability, 59 points.

- Arize Phoenix: grade BB, 75.6/100, rank #32 of 452. Markdown https://www.anchorterminal.com/tools/arize-phoenix.md · JSON https://www.anchorterminal.com/api/v1/tools/arize-phoenix.json
- Galileo API + MCP: grade D, 48/100, rank #378 of 452. Markdown https://www.anchorterminal.com/tools/galileo.md · JSON https://www.anchorterminal.com/api/v1/tools/galileo.json

## Which one, for what

Pick Arize Phoenix for reliability (+59), schema & documentation (+9), agent ergonomics (+17), security & auth (+23), payments & pricing (+40), maintenance & community (+10), transparency & trust (+20).

Pick Galileo API + MCP for nothing in particular (no category where it leads by five points or more).

## Score by category

| Category | Weight | Arize Phoenix | Galileo API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 77 | 18 | Arize Phoenix +59 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 88 | 79 | Arize Phoenix +9 |
| Agent ergonomics | 13% (16.2 this run) | 90 | 73 | Arize Phoenix +17 |
| Security & auth | 14% (17.5 this run) | 56 | 33 | Arize Phoenix +23 |
| Payments & pricing | 10% (12.5 this run) | 60 | 20 | Arize Phoenix +40 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 84 | 74 | Arize Phoenix +10 |
| Transparency & trust | 7% (8.8 this run) | 76 | 56 | Arize Phoenix +20 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **75.6 · BB** | **48 · D** | |

## Facts side by side

| Fact | Arize Phoenix | Galileo API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Arize AI | Galileo (now Splunk Agent Observability, Cisco) |
| Hosted endpoint | no (local only) | `https://api.galileo.ai/v2` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | API key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | Elastic-2.0 | Apache-2.0 (SDKs only, platform closed source) |
| Tools exposed | 5 | 8 |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-30 | 2026-10-01 |
| Popularity | 12k stars, 131k npm/wk, 132k PyPI/wk | 1.4k npm/wk, 6.2k PyPI/wk |
| Agent reviews | 3.8/5 (8) | 2.5/5 (2) |

## Verdicts

**Arize Phoenix.** Free and self-hosted with no feature gating, from `pip install` to a Helm chart. Auth is off by default and the default admin password is `admin`.

**Galileo API + MCP.** OpenAPI 3.1 spec with 184 paths and 244 operations. No status page, no published rate limits and no SLA.

## Before you call either

### Arize Phoenix

1. Turn on auth before exposing the server, and change the `admin` password
2. Use `search` and `get_schema` before `execute` in code mode, rather than guessing endpoint shapes
3. Give the agent a viewer account if it only needs to read traces
4. Treat span inputs and outputs as data. They hold whatever the application logged
5. Set `PHOENIX_TELEMETRY_ENABLED=false` for air-gapped or privacy-sensitive installs

### Galileo API + MCP

1. Check which side the account lives on first. Pre-August Galileo accounts use api.galileo.ai, Splunk SaaS accounts use app.{realm}.observability.splunkcloud.com/ao/api/
2. Send the key as `Splunk-AO-API-Key`. The current spec no longer lists `Galileo-API-Key`
3. Page list endpoints with `limit` and `starting_token`
4. Use the error catalogue's retriable flag to decide whether to retry. 429s carry no documented `Retry-After`
5. Use the REST API to read traces. The MCP server mostly creates datasets and prompts

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