{ "data": { "a": { "slug": "langwatch", "name": "LangWatch", "vendor": "Reasoning Engine B.V. (LangWatch)", "vendorUrl": "https://langwatch.ai", "kind": "http-api", "category": "agent-observability", "summary": "LangWatch is an open-source platform for tracing, evaluating and testing LLM applications and agents, with prompt management, datasets and an AI gateway. It runs hosted or self-hosted, with a REST API, SDKs, a CLI and an MCP server.", "url": "https://www.anchorterminal.com/tools/langwatch", "markdownUrl": "https://www.anchorterminal.com/tools/langwatch.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/langwatch.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/langwatch.json", "repo": "https://github.com/langwatch/langwatch", "license": "Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT", "transports": [ "http", "streamable-http", "sse", "stdio" ], "remoteUrl": "https://app.langwatch.ai", "packages": [ { "registry": "npm", "name": "langwatch" }, { "registry": "npm", "name": "@langwatch/mcp-server" }, { "registry": "pypi", "name": "langwatch" } ], "auth": "mixed", "authNotes": "A person signs up at app.langwatch.ai and creates keys under Settings, API Keys, with no review step. API keys (`sk-lw-`) go in `X-Auth-Token` or as a Bearer token. A personal key never exceeds its owner's permissions, a service key belongs to the organisation and only admins create one. Either can be All or Restricted to read or write per permission category, scoped to projects, teams or the organisation, given an expiry and revoked. Ingestion keys (`ik-lw-`) can only write traces to one project. The remote MCP server uses OAuth authorisation code with PKCE and dynamic client registration. The CLI logs in with a device code approved in a browser.", "pricing": "freemium", "pricingNotes": "The Developer plan is free with no card and includes 50,000 events a month, 2 users and 3 scenarios, so an agent can start without a contract once a person has signed up. Growth is 29 euros per core seat a month with 200,000 events, then 5 euros per 100,000 events and 3 euros per GB kept beyond the included retention. Enterprise is sold through sales. Instant Evals cost $0.0546 per million input tokens, with a $1 budget on unpaid organisations. The pricing page has a currency switch and we read the euro prices only. Self-hosting under Apache 2.0 is free with no volume cap, and an Enterprise licence is priced per seat (https://langwatch.ai/pricing, https://langwatch.ai/docs/pricing.md).", "priceSummary": "Freemium", "where": "both", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the docs index, the OpenAPI document or the pricing page (checked 2026-10-09).", "endpoints": [] }, "toolCount": 101, "popularity": { "githubStars": 4925, "npmWeekly": 50105, "pypiWeekly": 87325, "asOf": "2026-10-09" }, "docsUrl": "https://langwatch.ai/docs/introduction", "llmsTxt": "https://langwatch.ai/docs/llms.txt", "openapi": "https://app.langwatch.ai/api/gateway/v1/openapi.json", "capabilities": [ "obs.traces", "obs.evals", "obs.prompts", "obs.datasets", "obs.gateway" ], "tags": [ "hosted", "freemium", "no-card", "open-source", "self-hosted", "mcp", "oauth", "llms-txt", "openapi", "opentelemetry", "python", "typescript", "go", "cli", "status-page", "eu-hosted" ], "lastRelease": "2026-10-02", "graded": true, "anchor": { "graded": true, "score": 65.5, "grade": "B", "agentReady": false, "rank": 291, "ranked": true, "rankOf": 842, "categoryRank": 7, "methodology": "0.4", "run": "2026-10-01", "scores": { "ergonomics": 67, "maintenance": 90, "payments": 40, "reliability": 53, "schema": 87, "security": 71, "transparency": 75 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-09" }, "negative": -2, "negativeNotes": [ "2026-08-19. Advisory GHSA-h25p-f8f6-2ccf, rated moderate. The standalone HTTP mode of `@langwatch/mcp-server` 0.7.0 to 1.0.0 authorised requests by session id alone and accepted an API key in the URL. Fixed in 2.0.0 on 7 August 2026 and flagged as a breaking change. The advisory says the default stdio mode and the hosted handler were never affected, so -2 (https://github.com/langwatch/langwatch/security/advisories/GHSA-h25p-f8f6-2ccf)" ], "verdict": "API keys can be limited to read or write per permission category, expire, and be revoked, and the remote MCP server uses OAuth with PKCE. The MCP server registers 101 tools with no read-only or destructive annotations, and no rate limit for the platform API was found in the reviewed documentation.", "bestFor": "Teams that want tracing, evaluations and simulated-user agent tests in one open-source product, hosted in the EU or self-hosted, and that drive it from a coding assistant through MCP or the CLI.", "strengths": [ "API keys take read or write per permission category, a project, team or organisation scope and an expiry. Ingestion keys can only write traces", "A public OpenAPI 3.1 document covers 328 operations and is served without a key, with llms.txt and a Markdown twin of every docs page", "Apache 2.0 platform with MIT SDKs and MCP server. Self-hosting has no volume cap, and every outbound call is documented with its off switch", "The free Developer plan needs no card and includes 50,000 events a month. Paid usage is published at 5 euros per 100,000 events", "Platform 3.20.1 shipped on 2 October 2026, with 21 platform releases dated since 11 July in the repository changelog" ], "weaknesses": [ "The MCP server registers 101 tools, deletes and key creation among them, with no toolsets and no `readOnlyHint` or `destructiveHint` annotations in the source", "No request rate limit for the platform API was found in the reviewed documentation. Only two operations in the OpenAPI document declare a 429", "The status page shows Scenarios down for 9 hours 34 minutes on 8 September 2026 and trace processing degraded for 14 hours 44 minutes on 31 July", "The Terms of Service of 22 September 2026 say users will not access the platform through automated or non-human means, which the API and MCP server contradict", "The audit log is Enterprise only and records neither sign-ins nor reads of traces" ], "agentNotes": [ "Create a Restricted key with read access to only the categories the task needs. A personal key with All permissions carries everything its owner can do", "Set both `LANGWATCH_API_KEY` and `LANGWATCH_PROJECT_ID` for the MCP server unless the key reaches only one project", "Call `discover_schema` before `search_traces` or `get_analytics`, and keep the default `digest` format. `json` returns the full raw trace", "Allowlist MCP tools in the client. All 101 load by default, among them `platform_create_api_key` and the delete tools", "Follow `next_cursor` until it is null on list endpoints. A full page does not mean more rows exist" ], "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": 65.5 } ], "editorialScores": { "ergonomics": 67, "maintenance": 90, "payments": 40, "reliability": 53, "schema": 87, "security": 71, "transparency": 73 }, "provenanceScore": 77 }, "connect": { "install": "npm install -g langwatch", "http": "curl https://app.langwatch.ai/api/gateway/v1/openapi.json", "claudeCode": "claude mcp add langwatch --env LANGWATCH_API_KEY=sk-lw-... --env LANGWATCH_PROJECT_ID=your-project-id -- npx -y @langwatch/mcp-server", "config": { "mcpServers": { "langwatch": { "args": [ "-y", "@langwatch/mcp-server" ], "command": "npx", "env": { "LANGWATCH_API_KEY": "sk-lw-...", "LANGWATCH_PROJECT_ID": "your-project-id" } } } } }, "letme": { "capability": "https://letme.dev/obs.traces", "tool": "https://letme.dev/langwatch" }, "area": "developer", "unitPrices": [ { "item": "Instant Evals, judge input tokens", "unit": "1m-tokens", "usd": 0.0546, "note": "Output is free. Unpaid organisations have a $1 budget in total" } ], "provenance": { "legalEntity": "Reasoning Engine B.V. (doing business as LangWatch)", "domain": "langwatch.ai", "domainRegistered": "2023-09-17", "endpointOnVendorDomain": true, "terms": "https://langwatch.ai/legal/terms-conditions", "privacy": "https://langwatch.ai/legal/privacy-policy", "statusPage": "https://status.langwatch.ai", "changelog": "https://langwatch.ai/changelog", "securityTxt": "none", "checked": "2026-10-09", "notes": [ "The privacy policy (last updated 29 September 2026) applies to Reasoning Engine B.V., doing business as LangWatch, and covers the website and the Cloud Service. The Terms of Service (last updated 22 September 2026) cover the platform and the on-premise product.", "The terms page names the entity as Reasoning Engines B.V. in its heading and Reasoning Engine B.V. in its definitions, gives Singel 126, Amsterdam as the registered office and Herengracht 551, Amsterdam as the contact address. The site footer reads LangWatch B.V.", "The API, the hosted MCP server and the OpenAPI document are served from app.langwatch.ai. Hosted services for self-hosted installs with a licence use connect.langwatch.ai and gateway.langwatch.ai.", "https://langwatch.ai/.well-known/security.txt returns the website's HTML shell, not a security.txt file. SECURITY.md in the repository gives security@langwatch.ai and GitHub private reporting.", "RDAP for langwatch.ai gives a registration date of 2023-09-17 and GoDaddy.com, LLC as registrar.", "The trust report and sub-processor list are on app.eu.vanta.com, whose robots.txt disallows every path, so we did not read them." ], "score": 77 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/langwatch.json", "live": { "slug": "langwatch", "probe": { "target": "https://app.langwatch.ai", "method": "get", "lastAt": "2026-10-09T10:14:18.723958793Z", "lastOk": true, "lastStatus": 200, "lastMs": 128, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 85, "p95ms24h": 135, "samples24h": 28, "samples30d": 28, "days": [ { "date": "2026-10-09", "probes": 28, "ok": 28 } ] }, "vendorStatus": { "page": "https://status.langwatch.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-10-09T07:58:07.342247188Z" }, "updatedAt": "2026-10-09T10:14:18.723958793Z" } }, "answer": "Prefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust.", "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": 286, "ranked": true, "rankOf": 842, "categoryRank": 5, "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 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/prefactor.json", "live": { "slug": "prefactor", "probe": { "target": "https://app.prefactorai.com/api/v1", "method": "get", "lastAt": "2026-10-09T10:14:24.465685852Z", "lastOk": true, "lastStatus": 404, "lastMs": 173, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 318, "p95ms24h": 399, "samples24h": 159, "samples30d": 159, "days": [ { "date": "2026-10-08", "probes": 50, "ok": 50 }, { "date": "2026-10-09", "probes": 109, "ok": 109 } ] }, "vendorStatus": { "page": "https://status.prefactor.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-10-09T07:58:26.891368591Z" }, "updatedAt": "2026-10-09T10:14:24.465685852Z" } }, "facts": [ { "a": "HTTP API", "b": "HTTP API", "name": "Kind" }, { "a": "Reasoning Engine B.V. (LangWatch)", "b": "Prefactor Pty Ltd", "name": "Vendor" }, { "a": "https://app.langwatch.ai", "b": "https://app.prefactorai.com/api/v1", "name": "Hosted endpoint" }, { "a": "HTTP, Streamable HTTP, SSE (legacy), stdio", "b": "HTTP", "name": "Transports" }, { "a": "OAuth or key", "b": "API key", "name": "Auth" }, { "a": "Freemium", "b": "Freemium", "name": "Pricing" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT", "b": "Proprietary hosted service. The TypeScript and Python SDKs and the CLI are MIT", "name": "Licence" }, { "a": "101", "b": "none", "name": "Tools exposed" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "2026-10-02", "b": "2026-09-13", "name": "Last release" }, { "a": "2026-09-22", "b": "no document linked", "name": "Terms last updated" }, { "a": "2026-09-29", "b": "couldn't be read", "name": "Privacy policy last updated" }, { "a": "not found in the text", "b": "", "name": "Customer content may train models" }, { "a": "yes", "b": "", "name": "Terms restrict automated access" }, { "a": "not found in the text", "b": "", "name": "Terms restrict benchmarking" }, { "a": "yes", "b": "", "name": "Terms or service can change without notice" }, { "a": "not found in the text", "b": "", "name": "Arbitration or class-action waiver" }, { "a": "4.9k stars, 50k npm/wk, 87k PyPI/wk", "b": "3 stars, 19 npm/wk, 28 PyPI/wk", "name": "Popularity" } ], "faq": [ { "answer": "Prefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust.", "question": "Which is better for AI agents, LangWatch or Prefactor?" }, { "answer": "LangWatch takes an API key or an OAuth sign-in. Prefactor needs an API key.", "question": "Do LangWatch and Prefactor need an API key?" }, { "answer": "Yes. LangWatch has a hosted endpoint at https://app.langwatch.ai and Prefactor at https://app.prefactorai.com/api/v1.", "question": "Can an agent call LangWatch and Prefactor without installing anything?" }, { "answer": "LangWatch is open source (Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT). No open-source release is listed for Prefactor.", "question": "Are LangWatch and Prefactor open source?" } ], "goodFor": [ { "aheadOn": [ "Schema \u0026 documentation, 87 against 80", "Security \u0026 auth, 71 against 56", "Maintenance \u0026 community, 90 against 82", "Transparency \u0026 trust, 75 against 42" ], "also": [ "Runs on your own machine", "Open source" ], "goodFor": "Teams that want tracing, evaluations and simulated-user agent tests in one open-source product, hosted in the EU or self-hosted, and that drive it from a coding assistant through MCP or the CLI.", "slug": "langwatch", "watchFor": "The MCP server registers 101 tools, deletes and key creation among them, with no toolsets and no `readOnlyHint` or `destructiveHint` annotations in the source" }, { "aheadOn": [ "Reliability, 78 against 53", "Agent ergonomics, 88 against 67" ], "also": null, "goodFor": "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.", "slug": "prefactor", "watchFor": "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" } ], "job": { "capability": "obs.traces", "name": "Obs traces" }, "others": [ { "json": "https://www.anchorterminal.com/compare/arize-phoenix-vs-langwatch.json", "title": "Arize Phoenix vs LangWatch", "url": "https://www.anchorterminal.com/compare/arize-phoenix-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor.json", "title": "Arize Phoenix vs Prefactor", "url": "https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/baserun-vs-langwatch.json", "title": "Baserun vs LangWatch", "url": "https://www.anchorterminal.com/compare/baserun-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/baserun-vs-prefactor.json", "title": "Baserun vs Prefactor", "url": "https://www.anchorterminal.com/compare/baserun-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/braintrust-vs-langwatch.json", "title": "Braintrust API + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/braintrust-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/braintrust-vs-prefactor.json", "title": "Braintrust API + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/braintrust-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/galileo-vs-langwatch.json", "title": "Galileo API + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/galileo-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/galileo-vs-prefactor.json", "title": "Galileo API + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/galileo-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/helicone-vs-langwatch.json", "title": "Helicone AI Gateway + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/helicone-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/helicone-vs-prefactor.json", "title": "Helicone AI Gateway + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/helicone-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/honeyhive-vs-langwatch.json", "title": "HoneyHive vs LangWatch", "url": "https://www.anchorterminal.com/compare/honeyhive-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/honeyhive-vs-prefactor.json", "title": "HoneyHive vs Prefactor", "url": "https://www.anchorterminal.com/compare/honeyhive-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/laminar-vs-langwatch.json", "title": "Laminar API + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/laminar-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/laminar-vs-prefactor.json", "title": "Laminar API + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/laminar-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/langfuse-vs-langwatch.json", "title": "Langfuse API + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/langfuse-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/langfuse-vs-prefactor.json", "title": "Langfuse API + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/langfuse-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/langsmith-vs-langwatch.json", "title": "LangSmith API + MCP vs LangWatch", "url": "https://www.anchorterminal.com/compare/langsmith-vs-langwatch" }, { "json": "https://www.anchorterminal.com/compare/langsmith-vs-prefactor.json", "title": "LangSmith API + MCP vs Prefactor", "url": "https://www.anchorterminal.com/compare/langsmith-vs-prefactor" }, { "json": "https://www.anchorterminal.com/compare/langwatch-vs-respan.json", "title": "LangWatch vs Respan API + MCP", "url": "https://www.anchorterminal.com/compare/langwatch-vs-respan" }, { "json": "https://www.anchorterminal.com/compare/langwatch-vs-wandb-weave.json", "title": "LangWatch vs W\u0026B Weave", "url": "https://www.anchorterminal.com/compare/langwatch-vs-wandb-weave" }, { "json": "https://www.anchorterminal.com/compare/prefactor-vs-respan.json", "title": "Prefactor vs Respan API + MCP", "url": "https://www.anchorterminal.com/compare/prefactor-vs-respan" }, { "json": "https://www.anchorterminal.com/compare/prefactor-vs-wandb-weave.json", "title": "Prefactor vs W\u0026B Weave", "url": "https://www.anchorterminal.com/compare/prefactor-vs-wandb-weave" } ], "scores": [ { "by": 25, "edge": "prefactor", "key": "reliability", "langwatch": 53, "name": "Reliability", "prefactor": 78, "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "by": 7, "edge": "langwatch", "key": "schema", "langwatch": 87, "name": "Schema \u0026 documentation", "prefactor": 80, "weight": 13 }, { "by": 21, "edge": "prefactor", "key": "ergonomics", "langwatch": 67, "name": "Agent ergonomics", "prefactor": 88, "weight": 13 }, { "by": 15, "edge": "langwatch", "key": "security", "langwatch": 71, "name": "Security \u0026 auth", "prefactor": 56, "weight": 14 }, { "by": 0, "edge": "", "key": "payments", "langwatch": 40, "name": "Payments \u0026 pricing", "prefactor": 40, "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "by": 8, "edge": "langwatch", "key": "maintenance", "langwatch": 90, "name": "Maintenance \u0026 community", "prefactor": 82, "weight": 7 }, { "by": 33, "edge": "langwatch", "key": "transparency", "langwatch": 75, "name": "Transparency \u0026 trust", "prefactor": 42, "weight": 7 } ], "summary": "Prefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust. Both do obs traces.", "verdicts": { "langwatch": "API keys can be limited to read or write per permission category, expire, and be revoked, and the remote MCP server uses OAuth with PKCE. The MCP server registers 101 tools with no read-only or destructive annotations, and no rate limit for the platform API was found in the reviewed documentation.", "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." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/langwatch-vs-prefactor", "json": "https://www.anchorterminal.com/compare/langwatch-vs-prefactor.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/langwatch-vs-prefactor.md", "slim": "https://www.anchorterminal.com/compare/langwatch-vs-prefactor.min.md" }, "markdown": "Prefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust. Both do obs traces.\n\n- LangWatch: grade B, 65.5/100, rank #291 of 842. Markdown https://www.anchorterminal.com/tools/langwatch.md · JSON https://www.anchorterminal.com/api/v1/tools/langwatch.json\n- Prefactor: grade B, 65.6/100, rank #286 of 842. 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### LangWatch (B)\n\nGood for: Teams that want tracing, evaluations and simulated-user agent tests in one open-source product, hosted in the EU or self-hosted, and that drive it from a coding assistant through MCP or the CLI.\n\nAhead on:\n- Schema \u0026 documentation, 87 against 80\n- Security \u0026 auth, 71 against 56\n- Maintenance \u0026 community, 90 against 82\n- Transparency \u0026 trust, 75 against 42\n\nAlso in its favour:\n- Runs on your own machine\n- Open source\n\nWatch for: The MCP server registers 101 tools, deletes and key creation among them, with no toolsets and no `readOnlyHint` or `destructiveHint` annotations in the source\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- Reliability, 78 against 53\n- Agent ergonomics, 88 against 67\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 | LangWatch | Prefactor | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 53 | 78 | Prefactor +25 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 87 | 80 | LangWatch +7 |\n| Agent ergonomics | 13% (16.2 this run) | 67 | 88 | Prefactor +21 |\n| Security \u0026 auth | 14% (17.5 this run) | 71 | 56 | LangWatch +15 |\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) | 90 | 82 | LangWatch +8 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 75 | 42 | LangWatch +33 |\n| Negative events | ≤15 | -2 | -3 | |\n| **Total** | | **65.5 · B** | **65.6 · B** | |\n\n## Facts side by side\n\n| Fact | LangWatch | Prefactor |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Reasoning Engine B.V. (LangWatch) | Prefactor Pty Ltd |\n| Hosted endpoint | `https://app.langwatch.ai` | `https://app.prefactorai.com/api/v1` |\n| Transports | HTTP, Streamable HTTP, SSE (legacy), stdio | HTTP |\n| Auth | OAuth or key | API key |\n| Pricing | Freemium | Freemium |\n| x402 | no | no |\n| Licence | Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT | Proprietary hosted service. The TypeScript and Python SDKs and the CLI are MIT |\n| Tools exposed | 101 | none |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-10-02 | 2026-09-13 |\n| Terms last updated | 2026-09-22 | no document linked |\n| Privacy policy last updated | 2026-09-29 | couldn't be read |\n| Customer content may train models | not found in the text | |\n| Terms restrict automated access | yes | |\n| Terms restrict benchmarking | not found in the text | |\n| Terms or service can change without notice | yes | |\n| Arbitration or class-action waiver | not found in the text | |\n| Popularity | 4.9k stars, 50k npm/wk, 87k PyPI/wk | 3 stars, 19 npm/wk, 28 PyPI/wk |\n\n## Verdicts\n\n**LangWatch.** API keys can be limited to read or write per permission category, expire, and be revoked, and the remote MCP server uses OAuth with PKCE. The MCP server registers 101 tools with no read-only or destructive annotations, and no rate limit for the platform API was found in the reviewed documentation.\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### LangWatch\n\n1. Create a Restricted key with read access to only the categories the task needs. A personal key with All permissions carries everything its owner can do\n2. Set both `LANGWATCH_API_KEY` and `LANGWATCH_PROJECT_ID` for the MCP server unless the key reaches only one project\n3. Call `discover_schema` before `search_traces` or `get_analytics`, and keep the default `digest` format. `json` returns the full raw trace\n4. Allowlist MCP tools in the client. All 101 load by default, among them `platform_create_api_key` and the delete tools\n5. Follow `next_cursor` until it is null on list endpoints. A full page does not mean more rows exist\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, LangWatch or Prefactor?\n\nPrefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust.\n\n### Do LangWatch and Prefactor need an API key?\n\nLangWatch takes an API key or an OAuth sign-in. Prefactor needs an API key.\n\n### Can an agent call LangWatch and Prefactor without installing anything?\n\nYes. LangWatch has a hosted endpoint at https://app.langwatch.ai and Prefactor at https://app.prefactorai.com/api/v1.\n\n### Are LangWatch and Prefactor open source?\n\nLangWatch is open source (Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT). No open-source release is listed for Prefactor.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/langwatch-vs-prefactor.json, and with the fewest tokens: https://www.anchorterminal.com/compare/langwatch-vs-prefactor.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"langwatch\", \"b\": \"prefactor\"}`. From a terminal: `anchor compare langwatch prefactor`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/langwatch.json and https://www.anchorterminal.com/api/v1/tools/prefactor.json\n\n## Other comparisons with LangWatch or Prefactor\n\n- [Arize Phoenix vs LangWatch](https://www.anchorterminal.com/compare/arize-phoenix-vs-langwatch.md)\n- [Arize Phoenix vs Prefactor](https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor.md)\n- [Baserun vs LangWatch](https://www.anchorterminal.com/compare/baserun-vs-langwatch.md)\n- [Baserun vs Prefactor](https://www.anchorterminal.com/compare/baserun-vs-prefactor.md)\n- [Braintrust API + MCP vs LangWatch](https://www.anchorterminal.com/compare/braintrust-vs-langwatch.md)\n- [Braintrust API + MCP vs Prefactor](https://www.anchorterminal.com/compare/braintrust-vs-prefactor.md)\n- [Galileo API + MCP vs LangWatch](https://www.anchorterminal.com/compare/galileo-vs-langwatch.md)\n- [Galileo API + MCP vs Prefactor](https://www.anchorterminal.com/compare/galileo-vs-prefactor.md)\n- [Helicone AI Gateway + MCP vs LangWatch](https://www.anchorterminal.com/compare/helicone-vs-langwatch.md)\n- [Helicone AI Gateway + MCP vs Prefactor](https://www.anchorterminal.com/compare/helicone-vs-prefactor.md)\n- [HoneyHive vs LangWatch](https://www.anchorterminal.com/compare/honeyhive-vs-langwatch.md)\n- [HoneyHive vs Prefactor](https://www.anchorterminal.com/compare/honeyhive-vs-prefactor.md)\n- [Laminar API + MCP vs LangWatch](https://www.anchorterminal.com/compare/laminar-vs-langwatch.md)\n- [Laminar API + MCP vs Prefactor](https://www.anchorterminal.com/compare/laminar-vs-prefactor.md)\n- [Langfuse API + MCP vs LangWatch](https://www.anchorterminal.com/compare/langfuse-vs-langwatch.md)\n- [Langfuse API + MCP vs Prefactor](https://www.anchorterminal.com/compare/langfuse-vs-prefactor.md)\n- [LangSmith API + MCP vs LangWatch](https://www.anchorterminal.com/compare/langsmith-vs-langwatch.md)\n- [LangSmith API + MCP vs Prefactor](https://www.anchorterminal.com/compare/langsmith-vs-prefactor.md)\n- [LangWatch vs Respan API + MCP](https://www.anchorterminal.com/compare/langwatch-vs-respan.md)\n- [LangWatch vs W\u0026B Weave](https://www.anchorterminal.com/compare/langwatch-vs-wandb-weave.md)\n- [Prefactor vs Respan API + MCP](https://www.anchorterminal.com/compare/prefactor-vs-respan.md)\n- [Prefactor vs W\u0026B Weave](https://www.anchorterminal.com/compare/prefactor-vs-wandb-weave.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-10-09", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.4", "openapi": "https://www.anchorterminal.com/openapi.json", "preview": false, "run": "2026-10-01", "runLabel": "October 2026 research run" }, "page": { "breadcrumbs": [ { "name": "Home", "url": "https://www.anchorterminal.com/" }, { "name": "Compare", "url": "https://www.anchorterminal.com/compare/" }, { "name": "LangWatch vs Prefactor", "url": "" } ], "description": "Prefactor and LangWatch score within a point of each other on agent readiness, 65.6 (B) and 65.5 (B). LangWatch leads on schema \u0026 documentation, security \u0026 auth, maintenance \u0026 community and transparency \u0026 trust. Both do obs traces. Category scores, facts, verdicts and agent…", "facts": [ "LangWatch B 65.5", "Prefactor B 65.6", "scores" ], "h1": "LangWatch vs Prefactor", "image": "https://www.anchorterminal.com/assets/og/compare-langwatch-vs-prefactor.png", "path": "/compare/langwatch-vs-prefactor", "published": "2026-10-01", "section": "tools", "title": "LangWatch vs Prefactor for AI agents, B 65.5 vs B 65.6", "toc": null, "updated": "2026-10-09", "url": "https://www.anchorterminal.com/compare/langwatch-vs-prefactor" }, "tokens": { "markdown": 2550, "slim": 780 }, "version": 1 }