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What is LangSight?

Agents call three types of things:
  1. MCP servers (postgres-mcp, jira-mcp, slack-mcp) — via the MCP protocol
  2. Non-MCP tools (Stripe API, Sendgrid, Python functions, code execution) — direct calls
  3. Sub-agents (agent-to-agent handoffs in multi-agent workflows)
LangSight observes all three. Instrument once at the agent level and you automatically capture everything the agent touched — MCP or not. The server_name field in a ToolCallSpan can be “stripe-api”, “sendgrid”, “openai-api”, or “postgres-mcp”. It is not locked to MCP servers. MCP servers get extra depth because the MCP protocol is standard and inspectable — proactive health checks, security scanning, schema drift detection, and alerting on DOWN/DEGRADED state. Non-MCP tools appear in every trace but cannot be proactively health-checked (no standard protocol to ping).

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What you can do per tool type

Tool typeObserve callsHealth checkSecurity scanCost tracking
MCP serversYesYesYesYes
HTTP APIs (Stripe, Sendgrid, etc.)YesNoNoYes
Python functionsYesNoNoYes
Sub-agentsYesNoNoYes

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Example: mixed agent session

Agent Session: sess-abc123  (support-agent)
│
├── [MCP]      postgres-mcp / query          42ms  ✓  $0.001
├── [MCP]      jira-mcp / get_issue           89ms  ✓  $0.001
├── [HTTP API] stripe-api / charge_card      340ms  ✓  $0.005
├── [function] calculate_discount              0ms  ✓  $0.000
├── [MCP]      slack-mcp / post_message         —   ✗  timeout
└── [sub-agent] billing-agent
    ├── [MCP]  crm-mcp / update_customer     120ms  ✓  $0.001
    └── [HTTP] sendgrid / send_email          89ms  ✓  $0.002

Total: 680ms | 7 calls | 1 failure | $0.011
MCP servers: 4 of 7 calls (health-checked and security-scanned independently)
LangSight gives you:

Agent Session Traces

Full ordered trace for every agent session — MCP calls, HTTP API calls, function calls, sub-agent handoffs — all in one view with cost per session.

Multi-Agent Support

When Agent A hands off to Agent B which calls Agent C, trace the full tree. Parent-child span relationships (same model as OpenTelemetry).

MCP Health Monitoring

Proactive availability checks, latency tracking, and schema drift detection for MCP servers. Unique: synthetic probes, not just passive recording.

MCP Security Scanning

CVE detection, OWASP MCP Top 10 audit, tool poisoning detection, and auth gap analysis — for MCP servers specifically.

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LangSight and Langfuse

LangSight is not a Langfuse replacement. They answer different questions:
LangfuseLangSight
What it tracesLLM calls — prompts, completions, token costsTool calls — MCP spans, latency, errors, cost
What it monitorsNothing (passive only)MCP server health — synthetic probes, schema drift
SecurityNoneCVE, OWASP MCP Top 10, tool poisoning, auth audit
Multi-agentAgent reasoning chainsAgent-to-agent handoffs via parent_span_id
Use them together. Langfuse shows the LLM decided to call postgres-mcp/query. LangSight shows that call took 4 seconds and failed because the connection pool was exhausted.

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How it works

Your agents                LangSight
──────────                 ──────────────────────────────────────
CrewAI          ──SDK──►   POST /api/traces/spans
Pydantic AI     ──SDK──►   POST /api/agents/sessions
LibreChat       ──plugin►
Claude Desktop  ◄──health─ langsight mcp-health
                ◄──scan──  langsight security-scan
                ◄──trace─  langsight sessions
                ◄──rca───  langsight investigate

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Installation

# Install with uv (recommended)
uv tool install langsight

# Or with pip
pip install langsight

langsight init          # auto-discovers your MCP servers
langsight sessions      # view recent agent sessions with costs
langsight mcp-health    # check MCP server health

Quickstart →

Get from install to your first agent trace in 5 minutes.

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Integrations

LangSight works with every major MCP client and agent framework:
FrameworkIntegration
Claude DesktopAuto-discovered by langsight init
CursorAuto-discovered by langsight init
VS CodeAuto-discovered by langsight init
LibreChatNative plugin
LangChainLangSightLangChainCallback
LangflowLangSightLangChainCallback
LangGraphLangSightLangChainCallback
LangServeLangSightLangChainCallback
CrewAILangSightCrewAICallback
Pydantic AI@langsight_tool decorator
Any OTEL frameworkOTLP endpoint

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Open source

LangSight is Apache 2.0 licensed. The CLI, API, SDK, and all integrations are free and open source. 
git clone https://github.com/sumankalyan123/langsight