Head to head · Obs traces · October 2026 research run

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.

Which one, for what

No category where it leads by five points or more.

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

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)

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.

OpenAPI 3.1 spec with 184 paths and 244 operations. No status page, no published rate limits and no SLA.

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

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/
Send the key as Splunk-AO-API-Key. The current spec no longer lists Galileo-API-Key
Page list endpoints with limit and starting_token
Use the error catalogue's retriable flag to decide whether to retry. 429s carry no documented Retry-After
Use the REST API to read traces. The MCP server mostly creates datasets and prompts