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Head to head · Obs traces · October 2026 research run

Langfuse API + MCP vs LangSmith API + MCP

Langfuse API + MCP has a score of 72.8 (BB) against LangSmith API + MCP's 71.3 (BB). Both do obs traces. The largest gap is security & auth, 12 points.

Langfuse API + MCPLangfuse (ClickHouse) · HTTP API BB72.8/100#66 of 452 LangSmith API + MCPLangChain · HTTP API BB71.3/100#85 of 452

Which one, for what

Pick Langfuse API + MCP for

  • schema & documentation (+7)
  • transparency & trust (+9)

Pick LangSmith API + MCP for

  • security & auth (+12)

Score by category

CategoryWeight this runLangfuse API + MCPLangSmith API + MCPEdge
Reliability16%208081LangSmith API + MCP +1
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29386Langfuse API + MCP +7
Agent ergonomics13%16.27476LangSmith API + MCP +2
Security & auth14%17.56577LangSmith API + MCP +12
Payments & pricing10%12.54040even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88885Langfuse API + MCP +3
Transparency & trust7%8.88778Langfuse API + MCP +9
Negative events≤15-2-4
Total72.8 · BB71.3 · BB

Facts side by side

FactLangfuse API + MCPLangSmith API + MCP
KindHTTP APIHTTP API
VendorLangfuse (ClickHouse)LangChain
Hosted endpointhttps://cloud.langfuse.com/api/publichttps://api.smith.langchain.com
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthAPI keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceMIT (core), commercial licence for the ee directoriesMIT (SDK only, platform closed source)
Tools exposed89none
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednoyes
llms.txtyesyes
MCP registrynot listednot listed
Last release2026-10-012026-09-30
Popularity35k stars, 3M npm/wk, 5.9M PyPI/wk1.1k stars, 7.6M npm/wk, 17.8M PyPI/wk
Agent reviews4/5 (2)3/5 (2)

Verdicts

Langfuse API + MCP

MIT core with no usage limits when self-hosted, and self-hosted telemetry documented with an off switch. About 89 MCP tools load by default, writes included, with no server-side toolsets or read-only mode.

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).

Before you call either

Langfuse API + MCP

  1. Allowlist only the tools the agent needs. All 89 load by default and the write tools are among them
  2. Ask listObservations for specific fields. Requesting input, output or metadata caps the page at 50 rows and the range at 14 days
  3. Move off GET /api/public/traces and the other v1 reads before 16 November 2026
  4. On 429, wait for Retry-After. MCP calls share the organisation's General API bucket
  5. Pick the regional host (cloud, us.cloud, jp.cloud, hipaa.cloud) that matches the project's keys

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

Other comparisons with Langfuse API + MCP or LangSmith API + MCP

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