{
  "data": {
    "a": {
      "slug": "langfuse",
      "name": "Langfuse API + MCP",
      "vendor": "Langfuse (ClickHouse)",
      "vendorUrl": "https://langfuse.com",
      "kind": "http-api",
      "category": "agent-observability",
      "summary": "Open-source tracing, evaluation, prompt management and datasets for LLM apps and agents, built on OpenTelemetry.",
      "url": "https://www.anchorterminal.com/tools/langfuse",
      "markdownUrl": "https://www.anchorterminal.com/tools/langfuse.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/langfuse.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/langfuse.json",
      "repo": "https://github.com/langfuse/langfuse",
      "license": "MIT (core), commercial licence for the ee directories",
      "transports": [
        "http",
        "streamable-http"
      ],
      "remoteUrl": "https://cloud.langfuse.com/api/public",
      "packages": [
        {
          "registry": "pypi",
          "name": "langfuse"
        },
        {
          "registry": "npm",
          "name": "@langfuse/tracing"
        },
        {
          "registry": "npm",
          "name": "@langfuse/client"
        }
      ],
      "auth": "api-key",
      "authNotes": "Project-scoped key pair (public `pk-lf-...`, secret `sk-lf-...`) sent as HTTP Basic auth, for both the REST API and the MCP server at `/api/public/mcp`. Organisation-level keys exist for SCIM and admin APIs on Enterprise.",
      "pricing": "freemium",
      "pricingNotes": "Cloud Hobby is free with 50,000 units a month, 30 days of data and 2 users, no card. Core $29 a month with 100,000 units and 90 days, Pro $199 a month with 3 years of data, Enterprise $2,499 a month. Extra units cost $8 per 100,000 on paid plans, lower with volume. A unit is one trace, observation or score. Teams add-on $300 a month for SSO and fine-grained RBAC. Self-hosted open source is free with unlimited usage, you pay for your own Postgres, ClickHouse, Redis and blob storage. Self-hosted Enterprise is custom and sold on top of a ClickHouse plan (https://langfuse.com/pricing).",
      "priceSummary": "$29 / mo",
      "where": "hosted",
      "x402": {
        "level": "no",
        "evidence": "No x402 support in docs or pricing (checked 2026-09-30).",
        "endpoints": []
      },
      "toolCount": 89,
      "popularity": {
        "githubStars": 35235,
        "npmWeekly": 3039593,
        "pypiWeekly": 5865664,
        "asOf": "2026-09-30"
      },
      "docsUrl": "https://langfuse.com/docs",
      "llmsTxt": "https://langfuse.com/llms.txt",
      "openapi": "https://cloud.langfuse.com/generated/api/openapi.yml",
      "capabilities": [
        "obs.traces",
        "obs.evals",
        "obs.prompts",
        "obs.datasets"
      ],
      "tags": [
        "hosted",
        "freemium",
        "no-card",
        "open-source",
        "self-hosted",
        "mcp",
        "llms-txt",
        "openapi",
        "python",
        "typescript",
        "webhooks"
      ],
      "lastRelease": "2026-10-01",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 72.7,
        "grade": "BB",
        "agentReady": true,
        "rank": 88,
        "ranked": true,
        "rankOf": 722,
        "categoryRank": 2,
        "methodology": "0.4",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 74,
          "maintenance": 88,
          "payments": 40,
          "reliability": 80,
          "schema": 93,
          "security": 65,
          "transparency": 85
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "high",
          "date": "2026-10-01"
        },
        "negative": -2,
        "negativeNotes": [
          "2025-11-09 to 2026-01-21. Three moderate advisories, cross-organisation enumeration of member and invitation lists (GHSA-94hf-6gqq-pj69), SSO account takeover through CSRF or phishing (GHSA-w9pw-c549-5m6w) and an unauthenticated Slack OAuth install that could link Slack to any project (GHSA-pvq7-vvfj-p98x). All fixed and published, eight to eleven months old, so -2 (https://github.com/langfuse/langfuse/security/advisories)"
        ],
        "verdict": "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.",
        "bestFor": "Teams that want open source they can self-host or a predictable cloud bill, across tracing, evals, prompts and datasets.",
        "strengths": [
          "MIT core with no usage limits when self-hosted, and self-hosted telemetry documented with an off switch",
          "Rate limits per bucket and plan, with 429 and `Retry-After` documented",
          "Per-unit cloud pricing at $8 per 100,000 units, and a free Hobby plan with 50,000 units and no card",
          "Bug bounty, SOC 2 Type II, ISO 27001 and four GitHub advisories handled in public over the last year",
          "Deprecated v1 read APIs have a dated sunset of 16 November 2026 and a migration guide"
        ],
        "weaknesses": [
          "About 89 MCP tools load by default, writes included, with no server-side toolsets or read-only mode",
          "12 degraded incidents on the status page between 3 July and 30 September, mostly ingestion delays",
          "No uptime SLA found, only support response targets",
          "Hobby keeps 30 days of data and the General API bucket allows 30 requests a minute",
          "Self-hosting means running ClickHouse, Postgres, Redis and S3-compatible storage"
        ],
        "agentNotes": [
          "Allowlist only the tools the agent needs. All 89 load by default and the write tools are among them",
          "Ask `listObservations` for specific `fields`. Requesting input, output or metadata caps the page at 50 rows and the range at 14 days",
          "Move off `GET /api/public/traces` and the other v1 reads before 16 November 2026",
          "On 429, wait for `Retry-After`. MCP calls share the organisation's General API bucket",
          "Pick the regional host (cloud, us.cloud, jp.cloud, hipaa.cloud) that matches the project's keys"
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 2,
        "avgRating": 4,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "high",
            "grade": "BB",
            "methodology": "0.4",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 72.7
          }
        ],
        "editorialScores": {
          "ergonomics": 74,
          "maintenance": 88,
          "payments": 40,
          "reliability": 80,
          "schema": 93,
          "security": 65,
          "transparency": 91
        },
        "provenanceScore": 78
      },
      "connect": {
        "http": "curl -u \"$LANGFUSE_PUBLIC_KEY:$LANGFUSE_SECRET_KEY\" https://cloud.langfuse.com/api/public/projects",
        "claudeCode": "claude mcp add --transport http langfuse https://cloud.langfuse.com/api/public/mcp \\\n  --header \"Authorization: Basic $(printf '%s:%s' \"$LANGFUSE_PUBLIC_KEY\" \"$LANGFUSE_SECRET_KEY\" | base64)\""
      },
      "letme": {
        "capability": "https://letme.dev/obs.traces",
        "tool": "https://letme.dev/langfuse"
      },
      "area": "developer",
      "unitPrices": [
        {
          "item": "Core plan",
          "unit": "month",
          "usd": 29,
          "note": "100,000 units included, 90 days of data"
        },
        {
          "item": "Pro plan",
          "unit": "month",
          "usd": 199,
          "note": "100,000 units included, 3 years of data"
        },
        {
          "item": "Enterprise plan",
          "unit": "month",
          "usd": 2499,
          "note": "100,000 units included, audit logs, SCIM, SLAs"
        },
        {
          "item": "Teams add-on",
          "unit": "month",
          "usd": 300,
          "note": "SSO, SSO enforcement and fine-grained RBAC on Pro"
        }
      ],
      "provenance": {
        "legalEntity": "Langfuse GmbH (a ClickHouse, Inc. company)",
        "domain": "langfuse.com",
        "domainRegistered": "2023-04-20",
        "endpointOnVendorDomain": true,
        "terms": "https://clickhouse.com/legal/clickhouse-general-terms-and-conditions",
        "privacy": "https://langfuse.com/privacy",
        "statusPage": "https://status.langfuse.com",
        "changelog": "https://langfuse.com/changelog",
        "securityTxt": "none",
        "checked": "2026-09-30",
        "notes": [
          "The imprint names Langfuse GmbH in Berlin. The privacy notice is issued by ClickHouse, Inc. and langfuse.com/terms redirects to the ClickHouse general terms"
        ],
        "score": 78
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/langfuse.json",
      "live": {
        "slug": "langfuse",
        "probe": {
          "target": "https://cloud.langfuse.com/api/public",
          "method": "get",
          "lastAt": "2026-10-09T01:12:49.476439223Z",
          "lastOk": true,
          "lastStatus": 404,
          "lastMs": 51,
          "authRequired": false,
          "uptime24h": 100,
          "uptime30d": 100,
          "p50ms24h": 54,
          "p95ms24h": 88,
          "samples24h": 267,
          "samples30d": 2199,
          "days": [
            {
              "date": "2026-09-30",
              "probes": 35,
              "ok": 35
            },
            {
              "date": "2026-10-01",
              "probes": 276,
              "ok": 276
            },
            {
              "date": "2026-10-02",
              "probes": 248,
              "ok": 248
            },
            {
              "date": "2026-10-03",
              "probes": 271,
              "ok": 271
            },
            {
              "date": "2026-10-04",
              "probes": 272,
              "ok": 272
            },
            {
              "date": "2026-10-05",
              "probes": 272,
              "ok": 272
            },
            {
              "date": "2026-10-06",
              "probes": 272,
              "ok": 272
            },
            {
              "date": "2026-10-07",
              "probes": 272,
              "ok": 272
            },
            {
              "date": "2026-10-08",
              "probes": 268,
              "ok": 268
            },
            {
              "date": "2026-10-09",
              "probes": 13,
              "ok": 13
            }
          ]
        },
        "vendorStatus": {
          "page": "https://status.langfuse.com",
          "indicator": "none",
          "summary": "All Systems Operational",
          "checkedAt": "2026-10-09T01:07:37.617081854Z"
        },
        "versions": [
          {
            "registry": "github",
            "name": "langfuse/langfuse",
            "version": "v4.55.0",
            "released": "2026-10-08",
            "seenAt": "2026-10-08T16:18:24.588520565Z"
          },
          {
            "registry": "npm",
            "name": "@langfuse/client",
            "version": "5.13.1",
            "seenAt": "2026-10-08T16:18:22.622711734Z"
          },
          {
            "registry": "npm",
            "name": "@langfuse/tracing",
            "version": "5.13.1",
            "seenAt": "2026-10-08T16:18:21.541544154Z"
          },
          {
            "registry": "pypi",
            "name": "langfuse",
            "version": "4.17.0",
            "released": "2026-10-05",
            "seenAt": "2026-10-08T16:18:21.419024323Z"
          }
        ],
        "githubStars": 35528,
        "npmWeekly": 3268181,
        "pypiWeekly": 6331716,
        "securityTxt": {
          "url": "https://langfuse.com/.well-known/security.txt",
          "state": "none",
          "checkedAt": "2026-10-08T15:38:35.306691262Z"
        },
        "llmsTxt": {
          "url": "https://langfuse.com/llms.txt",
          "ok": true,
          "status": 200,
          "checkedAt": "2026-10-08T14:00:33.869864319Z"
        },
        "domain": {
          "domain": "langfuse.com",
          "registered": "2023-04-20",
          "source": "https://rdap.verisign.com/com/v1/domain/langfuse.com",
          "checkedAt": "2026-10-04T13:09:17.712369699Z"
        },
        "pages": [
          {
            "url": "https://langfuse.com/changelog",
            "kind": "changelog",
            "status": 404,
            "checkedAt": "2026-10-08T18:21:16.807292557Z",
            "changedAt": "0001-01-01T00:00:00Z"
          },
          {
            "url": "https://langfuse.com/blog/joining-clickhouse",
            "kind": "deprecations",
            "status": 304,
            "checkedAt": "2026-10-08T18:21:14.604548394Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "4e8ff98bb557"
          },
          {
            "url": "https://langfuse.com/pricing",
            "kind": "pricing",
            "status": 304,
            "checkedAt": "2026-10-08T18:21:18.752448188Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "fa6797a4f9e7"
          },
          {
            "url": "https://langfuse.com/privacy",
            "kind": "privacy",
            "status": 304,
            "checkedAt": "2026-10-08T18:21:20.652067587Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "9e1e582ef9a9"
          },
          {
            "url": "https://clickhouse.com/legal/clickhouse-general-terms-and-conditions",
            "kind": "terms",
            "status": 200,
            "checkedAt": "2026-10-08T18:16:08.788877158Z",
            "changedAt": "2026-10-06T16:06:19.636505735Z",
            "fingerprint": "1be14feaa85c"
          }
        ],
        "updatedAt": "2026-10-09T01:12:49.476439223Z"
      }
    },
    "answer": "Langfuse API + MCP scores 72.7 (BB) on agent readiness against Prefactor's 65.6 (B), and leads in 5 of 7 scored categories. Prefactor leads on agent ergonomics.",
    "b": {
      "slug": "prefactor",
      "name": "Prefactor",
      "vendor": "Prefactor Pty Ltd",
      "vendorUrl": "https://prefactor.tech",
      "kind": "http-api",
      "category": "agent-observability",
      "summary": "Prefactor is a hosted service that records AI agent runs as spans, classifies each run's data risk and stores quality evaluations. Agents and scripts reach it through an HTTP and WebSocket API, TypeScript and Python SDKs and a CLI.",
      "url": "https://www.anchorterminal.com/tools/prefactor",
      "markdownUrl": "https://www.anchorterminal.com/tools/prefactor.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/prefactor.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/prefactor.json",
      "repo": "https://github.com/prefactordev/typescript-sdk",
      "license": "Proprietary hosted service. The TypeScript and Python SDKs and the CLI are MIT",
      "transports": [
        "http"
      ],
      "remoteUrl": "https://app.prefactorai.com/api/v1",
      "packages": [
        {
          "registry": "npm",
          "name": "@prefactor/core"
        },
        {
          "registry": "npm",
          "name": "@prefactor/cli"
        },
        {
          "registry": "pypi",
          "name": "prefactor-core"
        }
      ],
      "auth": "api-key",
      "authNotes": "Self-serve. A person signs in at app.prefactorai.com and creates an API token, sent as `Authorization: Bearer \u003ctoken\u003e`. Account tokens reach every agent in the account. Deployment tokens are bound to one agent in one environment. The OpenAPI document adds a `role` of `read_only` or `full_access` (the default) and an `expires_at` that defaults to two years. Tokens can be suspended, reactivated and revoked. `POST /api_token` mints tokens with an existing token.",
      "pricing": "freemium",
      "pricingNotes": "Free Dev plan with 5,000 spans a month, up to 3 agents and 7-day retention, no card required, so an agent's owner can start without a contract. Startup is $49 a month ($499 a year) with 15,000 spans, then $0.0025 a span. Scaleup is $199 a month ($2,000 a year) with 100,000 spans, then $2.50 per 1,000 spans monthly or $2.00 on the annual plan. Enterprise, from 4 million spans a month, is by quote. A span is one LLM call, tool call, message turn or custom step. Seats are unlimited on every plan (https://prefactor.tech/pricing).",
      "priceSummary": "$49 / mo",
      "where": "hosted",
      "x402": {
        "level": "no",
        "evidence": "No x402, MPP or L402 in the docs, the OpenAPI document or the pricing page (checked 2026-10-08).",
        "endpoints": []
      },
      "toolCount": null,
      "popularity": {
        "githubStars": 3,
        "npmWeekly": 19,
        "pypiWeekly": 28,
        "asOf": "2026-10-08"
      },
      "docsUrl": "https://docs.prefactor.ai",
      "llmsTxt": "https://docs.prefactor.ai/llms.txt",
      "openapi": "https://app.prefactorai.com/api/v1/openapi",
      "capabilities": [
        "obs.traces",
        "obs.evals"
      ],
      "tags": [
        "hosted",
        "freemium",
        "no-card",
        "llms-txt",
        "openapi",
        "python",
        "typescript",
        "closed-source",
        "enterprise",
        "status-page"
      ],
      "lastRelease": "2026-09-13",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 65.6,
        "grade": "B",
        "agentReady": false,
        "rank": 253,
        "ranked": true,
        "rankOf": 722,
        "categoryRank": 4,
        "methodology": "0.4",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 88,
          "maintenance": 82,
          "payments": 40,
          "reliability": 78,
          "schema": 80,
          "security": 56,
          "transparency": 42
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-08"
        },
        "negative": -3,
        "negativeNotes": [
          "2026-10-08. The pricing page lists 'Hold, approve or block in real time' and PII detection on every plan, and the security page lists manual approval workflows and fine-grained RBAC. The vendor's own docs say crossing a risk threshold does not block or terminate a run, that Prefactor does not detect sensitive data, and that accounts have no role-based permissions. The OpenAPI and OpenRPC documents have no approval operation. Counted as a misleading claim (-3). The docs may lag the product, since the API has hosted judge operations they do not describe (https://prefactor.tech/pricing, https://prefactor.tech/security, https://docs.prefactor.ai/llms-full.txt)."
        ],
        "verdict": "The public OpenAPI document lists 157 operations, each accepting an idempotency key, and tokens can be read-only or bound to one agent deployment. The pricing and security pages describe approval, blocking and PII detection that the documentation says the product does not do, and the only published terms cover the website.",
        "bestFor": "A team that wants an auditable record of agent runs with declared data-risk labels, quality payloads from its own evaluations and a remote stop signal.",
        "strengths": [
          "Public OpenAPI 3.0 document with 157 operations and an OpenRPC document with 159 WebSocket methods, both fetched without a login",
          "Every write accepts an `idempotency_key`, and `POST /bulk` can be retried whole because a reused key fails only its own item",
          "Tokens are scoped to the account or to one agent deployment, carry a `read_only` or `full_access` role and an expiry, and can be suspended or revoked",
          "A 429 response carries `Retry-After` and `retry_after_ms`, and both SDKs retry with exponential backoff and jitter",
          "The free Dev plan includes 5,000 spans a month with no card, and the overage price per span is published"
        ],
        "weaknesses": [
          "The pricing page lists hold, approve or block and PII detection on every plan, while the docs say a risk threshold blocks nothing and that Prefactor does not detect sensitive data",
          "No approval operation exists in the OpenAPI or OpenRPC documents. The documented control is a cooperative terminate signal the agent's own code must obey",
          "The published terms of service cover the website. No service agreement, DPA, sub-processor list or SLA text was found",
          "Rate limits are described by scope with no numbers",
          "No security.txt and no certification held. The security page says SOC 2 Type II is in progress"
        ],
        "agentNotes": [
          "Send requests to `https://app.prefactorai.com/api/v1` with `Authorization: Bearer \u003ctoken\u003e`. The API host is not on the `prefactor.tech` or `prefactor.ai` domains",
          "Ask for a deployment-scoped token, or an account token created with `role` set to `read_only`, since the default role is `full_access` with a two-year expiry",
          "Pass `redacted: true` on span list and detail queries, because the API returns marked sensitive values unless asked otherwise",
          "On 429 wait for `retry_after_ms`. Limits use one-minute windows and the SDKs' default retries ignore the server's hint",
          "Treat terminate as a request. Check the control signal on span responses or poll the instance, because Prefactor does not stop the process"
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 0,
        "avgRating": 0,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "medium",
            "grade": "B",
            "methodology": "0.4",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 65.6
          }
        ],
        "editorialScores": {
          "ergonomics": 88,
          "maintenance": 82,
          "payments": 40,
          "reliability": 78,
          "schema": 80,
          "security": 56,
          "transparency": 34
        },
        "provenanceScore": 50
      },
      "connect": {
        "install": "npm install @prefactor/core",
        "http": "curl https://app.prefactorai.com/api/v1/agent \\\n  -H \"Authorization: Bearer $PREFACTOR_API_TOKEN\""
      },
      "letme": {
        "capability": "https://letme.dev/obs.traces",
        "tool": "https://letme.dev/prefactor"
      },
      "area": "developer",
      "unitPrices": [
        {
          "item": "Startup plan",
          "unit": "month",
          "usd": 49,
          "note": "15,000 spans included, 3-month retention"
        },
        {
          "item": "Scaleup plan",
          "unit": "month",
          "usd": 199,
          "note": "100,000 spans included, 12-month retention"
        },
        {
          "item": "Span beyond the Startup allowance",
          "unit": "record",
          "usd": 0.0025
        },
        {
          "item": "Span beyond the Scaleup allowance",
          "unit": "record",
          "usd": 0.0025,
          "note": "$2.50 per 1,000 on monthly billing, $2.00 on annual"
        }
      ],
      "provenance": {
        "legalEntity": "Prefactor Pty Ltd",
        "domain": "prefactor.tech",
        "domainRegistered": "2024-10-16",
        "endpointOnVendorDomain": false,
        "terms": "",
        "privacy": "https://prefactor.tech/privacy-policy",
        "statusPage": "https://status.prefactor.ai",
        "changelog": "https://prefactor.tech/changelog",
        "securityTxt": "none",
        "checked": "2026-10-08",
        "notes": [
          "prefactor.tech/llms.txt names Prefactor Pty Ltd, founded 2024, headquartered in Australia. The legal documents name the same entity and New South Wales law.",
          "`terms` is left out. The only published terms (last updated 17 March 2026) govern use of the website at prefactor.tech and are a generated website template. No service agreement, API terms or DPA was found on the site or in its sitemap.",
          "The privacy policy and terms pages are drawn by script from GetTerms. We read them from the feed the pages load (gettermscdn.com) and could render only the regional sections of the privacy policy, not its main body.",
          "The API answers at app.prefactorai.com, a third domain of the vendor's registered on 18 December 2025. The site is on prefactor.tech and the docs on docs.prefactor.ai.",
          "RDAP gives prefactor.tech a registration date of 16 October 2024 and an expiry of 16 October 2026, eight days after this check.",
          "prefactor.tech, app.prefactorai.com and docs.prefactor.ai each return 404 for /.well-known/security.txt. The security page asks for reports by email and promises an acknowledgement within 24 hours.",
          "status.prefactor.ai is an UptimeRobot page. We found no link to it on the site or docs pages we read."
        ],
        "score": 50
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          "method": "get",
          "lastAt": "2026-10-09T01:12:54.794079228Z",
          "lastOk": true,
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          "lastMs": 142,
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        "vendorStatus": {
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    "facts": [
      {
        "a": "HTTP API",
        "b": "HTTP API",
        "name": "Kind"
      },
      {
        "a": "Langfuse (ClickHouse)",
        "b": "Prefactor Pty Ltd",
        "name": "Vendor"
      },
      {
        "a": "https://cloud.langfuse.com/api/public",
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        "a": "HTTP, Streamable HTTP",
        "b": "HTTP",
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        "a": "API key",
        "b": "API key",
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        "a": "no",
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      {
        "a": "2026-08-21",
        "b": "couldn't be read",
        "name": "Privacy policy last updated"
      },
      {
        "a": "not found in the text",
        "b": "",
        "name": "Customer content may train models"
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        "name": "Terms restrict automated access"
      },
      {
        "a": "yes",
        "b": "",
        "name": "Terms restrict benchmarking"
      },
      {
        "a": "not found in the text",
        "b": "",
        "name": "Terms or service can change without notice"
      },
      {
        "a": "not found in the text",
        "b": "",
        "name": "Arbitration or class-action waiver"
      },
      {
        "a": "35k stars, 3M npm/wk, 5.9M PyPI/wk",
        "b": "3 stars, 19 npm/wk, 28 PyPI/wk",
        "name": "Popularity"
      },
      {
        "a": "4/5 (2)",
        "b": "none",
        "name": "Agent reviews"
      }
    ],
    "faq": [
      {
        "answer": "Langfuse API + MCP scores 72.7 (BB) on agent readiness against Prefactor's 65.6 (B), and leads in 5 of 7 scored categories. Prefactor leads on agent ergonomics.",
        "question": "Which is better for AI agents, Langfuse API + MCP or Prefactor?"
      },
      {
        "answer": "Both need an API key.",
        "question": "Do Langfuse API + MCP and Prefactor need an API key?"
      },
      {
        "answer": "Yes. Langfuse API + MCP has a hosted endpoint at https://cloud.langfuse.com/api/public and Prefactor at https://app.prefactorai.com/api/v1.",
        "question": "Can an agent call Langfuse API + MCP and Prefactor without installing anything?"
      },
      {
        "answer": "Langfuse API + MCP is open source (MIT (core), commercial licence for the ee directories). No open-source release is listed for Prefactor.",
        "question": "Are Langfuse API + MCP and Prefactor open source?"
      }
    ],
    "goodFor": [
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        "aheadOn": [
          "Schema \u0026 documentation, 93 against 80",
          "Security \u0026 auth, 65 against 56",
          "Maintenance \u0026 community, 88 against 82",
          "Transparency \u0026 trust, 85 against 42"
        ],
        "also": [
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        "slug": "prefactor",
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        "key": "reliability",
        "langfuse": 80,
        "name": "Reliability",
        "prefactor": 78,
        "weight": 16
      },
      {
        "key": "performance",
        "name": "Performance",
        "pending": true,
        "weight": 10
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      {
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        "key": "schema",
        "langfuse": 93,
        "name": "Schema \u0026 documentation",
        "prefactor": 80,
        "weight": 13
      },
      {
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        "edge": "prefactor",
        "key": "ergonomics",
        "langfuse": 74,
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        "prefactor": 88,
        "weight": 13
      },
      {
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        "edge": "langfuse",
        "key": "security",
        "langfuse": 65,
        "name": "Security \u0026 auth",
        "prefactor": 56,
        "weight": 14
      },
      {
        "by": 0,
        "edge": "",
        "key": "payments",
        "langfuse": 40,
        "name": "Payments \u0026 pricing",
        "prefactor": 40,
        "weight": 10
      },
      {
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        "name": "Task success",
        "pending": true,
        "weight": 10
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      {
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        "edge": "langfuse",
        "key": "maintenance",
        "langfuse": 88,
        "name": "Maintenance \u0026 community",
        "prefactor": 82,
        "weight": 7
      },
      {
        "by": 43,
        "edge": "langfuse",
        "key": "transparency",
        "langfuse": 85,
        "name": "Transparency \u0026 trust",
        "prefactor": 42,
        "weight": 7
      }
    ],
    "summary": "Langfuse API + MCP scores 72.7 (BB) on agent readiness against Prefactor's 65.6 (B), and leads in 5 of 7 scored categories. Prefactor leads on agent ergonomics. Both do obs traces.",
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      "langfuse": "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.",
      "prefactor": "The public OpenAPI document lists 157 operations, each accepting an idempotency key, and tokens can be read-only or bound to one agent deployment. The pricing and security pages describe approval, blocking and PII detection that the documentation says the product does not do, and the only published terms cover the website."
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  "markdown": "Langfuse API + MCP scores 72.7 (BB) on agent readiness against Prefactor's 65.6 (B), and leads in 5 of 7 scored categories. Prefactor leads on agent ergonomics. Both do obs traces.\n\n- Langfuse API + MCP: grade BB, 72.7/100, rank #88 of 722. Markdown https://www.anchorterminal.com/tools/langfuse.md · JSON https://www.anchorterminal.com/api/v1/tools/langfuse.json\n- Prefactor: grade B, 65.6/100, rank #253 of 722. Markdown https://www.anchorterminal.com/tools/prefactor.md · JSON https://www.anchorterminal.com/api/v1/tools/prefactor.json\n\n## Which one, for what\n\n### Langfuse API + MCP (BB)\n\nGood for: Teams that want open source they can self-host or a predictable cloud bill, across tracing, evals, prompts and datasets.\n\nAhead on:\n- Schema \u0026 documentation, 93 against 80\n- Security \u0026 auth, 65 against 56\n- Maintenance \u0026 community, 88 against 82\n- Transparency \u0026 trust, 85 against 42\n\nAlso in its favour:\n- Agent-ready, a grade of BB or better\n- Open source\n\nWatch for: About 89 MCP tools load by default, writes included, with no server-side toolsets or read-only mode\n\n### Prefactor (B)\n\nGood for: A team that wants an auditable record of agent runs with declared data-risk labels, quality payloads from its own evaluations and a remote stop signal.\n\nAhead on:\n- Agent ergonomics, 88 against 74\n\nWatch for: The pricing page lists hold, approve or block and PII detection on every plan, while the docs say a risk threshold blocks nothing and that Prefactor does not detect sensitive data\n\n\n## Score by category\n\n| Category | Weight | Langfuse API + MCP | Prefactor | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 80 | 78 | Langfuse API + MCP +2 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 93 | 80 | Langfuse API + MCP +13 |\n| Agent ergonomics | 13% (16.2 this run) | 74 | 88 | Prefactor +14 |\n| Security \u0026 auth | 14% (17.5 this run) | 65 | 56 | Langfuse API + MCP +9 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 40 | even |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 88 | 82 | Langfuse API + MCP +6 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 85 | 42 | Langfuse API + MCP +43 |\n| Negative events | ≤15 | -2 | -3 | |\n| **Total** | | **72.7 · BB** | **65.6 · B** | |\n\n## Facts side by side\n\n| Fact | Langfuse API + MCP | Prefactor |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Langfuse (ClickHouse) | Prefactor Pty Ltd |\n| Hosted endpoint | `https://cloud.langfuse.com/api/public` | `https://app.prefactorai.com/api/v1` |\n| Transports | HTTP, Streamable HTTP | HTTP |\n| Auth | API key | API key |\n| Pricing | Freemium | Freemium |\n| x402 | no | no |\n| Licence | MIT (core), commercial licence for the ee directories | Proprietary hosted service. The TypeScript and Python SDKs and the CLI are MIT |\n| Tools exposed | 89 | none |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-10-01 | 2026-09-13 |\n| Terms last updated | 2026-06-24 | no document linked |\n| Privacy policy last updated | 2026-08-21 | couldn't be read |\n| Customer content may train models | not found in the text |  |\n| Terms restrict automated access | not found in the text |  |\n| Terms restrict benchmarking | yes |  |\n| Terms or service can change without notice | not found in the text |  |\n| Arbitration or class-action waiver | not found in the text |  |\n| Popularity | 35k stars, 3M npm/wk, 5.9M PyPI/wk | 3 stars, 19 npm/wk, 28 PyPI/wk |\n| Agent reviews | 4/5 (2) | none |\n\n## Verdicts\n\n**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.\n\n**Prefactor.** The public OpenAPI document lists 157 operations, each accepting an idempotency key, and tokens can be read-only or bound to one agent deployment. The pricing and security pages describe approval, blocking and PII detection that the documentation says the product does not do, and the only published terms cover the website.\n\n## Before you call either\n\n### Langfuse API + MCP\n\n1. Allowlist only the tools the agent needs. All 89 load by default and the write tools are among them\n2. Ask `listObservations` for specific `fields`. Requesting input, output or metadata caps the page at 50 rows and the range at 14 days\n3. Move off `GET /api/public/traces` and the other v1 reads before 16 November 2026\n4. On 429, wait for `Retry-After`. MCP calls share the organisation's General API bucket\n5. Pick the regional host (cloud, us.cloud, jp.cloud, hipaa.cloud) that matches the project's keys\n\n### Prefactor\n\n1. Send requests to `https://app.prefactorai.com/api/v1` with `Authorization: Bearer \u003ctoken\u003e`. The API host is not on the `prefactor.tech` or `prefactor.ai` domains\n2. Ask for a deployment-scoped token, or an account token created with `role` set to `read_only`, since the default role is `full_access` with a two-year expiry\n3. Pass `redacted: true` on span list and detail queries, because the API returns marked sensitive values unless asked otherwise\n4. On 429 wait for `retry_after_ms`. Limits use one-minute windows and the SDKs' default retries ignore the server's hint\n5. Treat terminate as a request. Check the control signal on span responses or poll the instance, because Prefactor does not stop the process\n\n## Questions\n\n### Which is better for AI agents, Langfuse API + MCP or Prefactor?\n\nLangfuse API + MCP scores 72.7 (BB) on agent readiness against Prefactor's 65.6 (B), and leads in 5 of 7 scored categories. Prefactor leads on agent ergonomics.\n\n### Do Langfuse API + MCP and Prefactor need an API key?\n\nBoth need an API key.\n\n### Can an agent call Langfuse API + MCP and Prefactor without installing anything?\n\nYes. Langfuse API + MCP has a hosted endpoint at https://cloud.langfuse.com/api/public and Prefactor at https://app.prefactorai.com/api/v1.\n\n### Are Langfuse API + MCP and Prefactor open source?\n\nLangfuse API + MCP is open source (MIT (core), commercial licence for the ee directories). No open-source release is listed for Prefactor.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/langfuse-vs-prefactor.json, and with the fewest tokens: https://www.anchorterminal.com/compare/langfuse-vs-prefactor.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"langfuse\", \"b\": \"prefactor\"}`. From a terminal: `anchor compare langfuse prefactor`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/langfuse.json and https://www.anchorterminal.com/api/v1/tools/prefactor.json\n\n## Other comparisons with Langfuse API + MCP or Prefactor\n\n- [Arize Phoenix vs Langfuse API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-langfuse.md)\n- [Arize Phoenix vs Prefactor](https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor.md)\n- [Baserun vs Langfuse API + MCP](https://www.anchorterminal.com/compare/baserun-vs-langfuse.md)\n- [Baserun vs Prefactor](https://www.anchorterminal.com/compare/baserun-vs-prefactor.md)\n- [Braintrust API + MCP vs Langfuse API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-langfuse.md)\n- [Braintrust API + MCP vs Prefactor](https://www.anchorterminal.com/compare/braintrust-vs-prefactor.md)\n- [Galileo API + MCP vs Langfuse API + MCP](https://www.anchorterminal.com/compare/galileo-vs-langfuse.md)\n- [Galileo API + MCP vs Prefactor](https://www.anchorterminal.com/compare/galileo-vs-prefactor.md)\n- [Helicone AI Gateway + MCP vs Langfuse API + MCP](https://www.anchorterminal.com/compare/helicone-vs-langfuse.md)\n- [Helicone AI Gateway + MCP vs Prefactor](https://www.anchorterminal.com/compare/helicone-vs-prefactor.md)\n- [HoneyHive vs Langfuse API + MCP](https://www.anchorterminal.com/compare/honeyhive-vs-langfuse.md)\n- [HoneyHive vs Prefactor](https://www.anchorterminal.com/compare/honeyhive-vs-prefactor.md)\n- [Laminar API + MCP vs Langfuse API + MCP](https://www.anchorterminal.com/compare/laminar-vs-langfuse.md)\n- [Laminar API + MCP vs Prefactor](https://www.anchorterminal.com/compare/laminar-vs-prefactor.md)\n- [Langfuse API + MCP vs LangSmith API + MCP](https://www.anchorterminal.com/compare/langfuse-vs-langsmith.md)\n- [Langfuse API + MCP vs Respan API + MCP](https://www.anchorterminal.com/compare/langfuse-vs-respan.md)\n- [LangSmith API + MCP vs Prefactor](https://www.anchorterminal.com/compare/langsmith-vs-prefactor.md)\n- [Prefactor vs Respan API + MCP](https://www.anchorterminal.com/compare/prefactor-vs-respan.md)\n",
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