Baserun vs LangSmith API + MCP

Baserun

SDKs were MIT licensed and the Python source is still public at github.com/baserun-ai/baserun-py. Service offline since late 2024. api.baserun.ai doesn't resolve and app.baserun.ai serves an expired certificate.

LangSmith API + MCP

Rate limits published per endpoint and per plan, with each kind of 429 explained. Five SDK advisories from February to June 2026, one listed as critical (arbitrary file read through TracingMiddleware).

Baserun

1. Don't install baserun from PyPI or npm. Nothing answers behind it
2. Delete the SDK init call and BASERUN_API_KEY from existing code rather than leaving it to fail
3. Ignore docs.baserun.ai. It describes a service that no longer runs and doesn't say so

LangSmith API + MCP

1. Batch run reads. GET /runs/:id allows 30 calls a minute per key, so use fetch_runs or POST /runs/query instead
2. Pass trace_id or min_start_time to fetch_runs and keep limit low. Results page by a 25,000-character budget
3. Don't call create_dataset or run_experiment over MCP to make changes. They return how-to text, not results
4. Send X-Api-Key and point at the regional host (eu., apac. or aws.api.smith.langchain.com) that matches the workspace
5. Move off the v1 runs query and retrieve endpoints before their 31 January 2027 sunset