Arize Phoenix vs Respan API + MCP

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.

Respan API + MCP

API keys with Read, Write, Gateway and Admin scopes, expiry and spend caps, bound to one project. 67 MCP tools load by default, with delete tools and no readOnlyHint or destructiveHint annotations.

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

Respan API + MCP

1. Create a key with only the Read scope for agents that analyse logs. New keys get Read, Write and Gateway by default
2. Set Respan-Enabled-Tools to a short list such as list_traces,get_trace_tree,list_logs. All 67 tools load otherwise
3. Pass filters to list_logs rather than paging through everything. The default window is the last hour
4. Call list_organizations first when results look empty over OAuth. Every tool acts on the active organisation only
5. Append .md to any docs URL for clean Markdown