# Flagsmith vs PostHog (slim)

> PostHog scores 67.4 (B) to Flagsmith's 61.2 (C) for feature flags. Prices, MCP, x402, uptime and agent notes side by side.

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- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
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PostHog scores 67.4 (B) on agent readiness against Flagsmith's 61.2 (C), and leads in 6 of 7 scored categories. Both do feature flags.

- Flagsmith: C 61.2, rank #620 of 1486 · https://www.anchorterminal.com/tools/flagsmith.min.md
- PostHog: B 67.4, rank #327 of 1486 · https://www.anchorterminal.com/tools/posthog.min.md
- Flagsmith, good for Feature flags and experiments for teams that want open source or self-hosting, managed by an agent through MCP. Also Runs on your own machine.
- PostHog, good for An agent that answers product questions in SQL or with funnel, retention and trends queries, and that manages feature flags, experiments and error tracking in the same project. Ahead on Reliability, 84 against 65; Schema & documentation, 81 against 67; Agent ergonomics, 78 against 55; Security & auth, 84 against 65; Maintenance & community, 89 against 83; Transparency & trust, 83 against 77. Also Free to start without a card.

| Category | Flagsmith | PostHog |
| --- | --- | --- |
| Reliability (16%) | 65 | 84 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 67 | 81 |
| Agent ergonomics (13%) | 55 | 78 |
| Security & auth (14%) | 65 | 84 |
| Payments & pricing (10%) | 40 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 83 | 89 |
| Transparency & trust (7%) | 77 | 83 |

| Fact (where they differ) | Flagsmith | PostHog |
| --- | --- | --- |
| Vendor | Bullet Train Ltd | PostHog Inc. |
| Hosted endpoint | `https://mcp.flagsmith.com` | `https://us.posthog.com` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Price for feature flags | not published | $0.0001 per transaction |
| Licence | BSD-3-Clause | MIT for the repository outside the `ee` directory, which has its own licence. PostHog Cloud is a hosted service under PostHog's terms |
| Tools exposed | 54 | 1183 |
| llms.txt | no | yes |
| MCP registry | not listed | `io.github.PostHog/mcp` |
| Last release | 2026-11-05 | 2026-10-30 |
| Terms last updated | 2026-09-01 | 2026-06-29 |
| Privacy policy last updated | 2023-10-01 | 2026-06-29 |
| Customer content may train models | not found in the text | yes, with an opt-out |
| Terms restrict benchmarking | not found in the text | yes |
| Popularity | 6.6k stars | 40k stars, 15.2M npm/wk |
| Agent reviews | none | 3.3/5 (4) |

Why the edge:
- Agent ergonomics, PostHog +23: Flagsmith 55 (54 tools, more than 30, with no toolsets or read-only subset; enterprise tools only appear where installed (5 of 25). List endpoints paginate with page and page_size (default 10) and filter by project, environment and search (14 of 20). Errors are Django REST Framework bodies with field messages, without a documented error code list (12 of 20). Every tool carries readOnlyHint, destructiveHint and idempotentHint derived from its HTTP method. No idempotency keys for POST (14 of 20). Few required parameters; official SDKs in more than a dozen languages, though they cover flag evaluation rather than the Management API (10 of 15). 5+14+12+14+10 = 55.); PostHog 78 (1,183 MCP tool definitions in the repository on 1 November 2026 (375 behind feature flags) is far past 30 (5). Add back 10 for CLI mode, which registers one `exec` tool to search, inspect and call the rest, and for the `features`, `tools` and read-only filters (15). Cursor pagination with next and previous links, SQL with `LIMIT` to 50,000 rows and keyset paging, though `OFFSET` is refused for personal API keys (18). Errors carry `type`, `code`, `detail` and `attr`, and the budget 429 names its code (17). Every MCP tool has readOnlyHint, destructiveHint and idempotentHint (638 read-only, 142 destructive), and 18 admin actions are split into prepare and execute steps. No idempotency keys on REST writes (15). SDKs in many languages, but they cover capture and flags, not the private API (13).)
- Reliability, PostHog +19: Flagsmith 65 (Graded on Flagsmith Cloud with the hosted lines. Statuspage at status.flagsmith.com with components for the Edge API, Admin API, dashboard and website (20). In the 90 days from 8 August, an Admin and SDK API outage on 28 October marked critical, posted at 21:56 UTC and resolved at 22:12 with no cause given, and a minor delay in processing flag changes on 10 September. The posted span of the outage is 16 minutes and its start isn't stated, so we read it as one serious incident under an hour (15 of 30). The Management API limit of 500 requests a minute is documented (15). No 429 handling, Retry-After or idempotency guidance was found in the docs (0). A public SLA commits to 99.95 per cent monthly uptime with service credits (10). The Management API is generally available, but the MCP docs call the server an early release, so half (5 of 10). 20+15+15+0+10+5 = 65.); PostHog 84 (Graded on PostHog Cloud with the hosted lines. Status page on incident.io at posthogstatus.com with per-region components, among them MCP Server and REST API Query endpoints (20). Its RSS feed lists 28 incidents and one maintenance window from 4 August to 27 October 2026. Analytics queries timed out or failed from 31 August to 2 September (load shed after about four hours), on 10 September and on 30 September, the US region saw API errors in parts of the application on 19 August, and parts of the app, the `/flags` endpoint and realtime destinations were degraded for 74 minutes on 22 October. Each hit one product, one region or some requests, so the record reads as minor incidents only (20). Rate limits published with numbers per endpoint class, counted per personal API key (15). The query read budget answers 429 with `Retry-After` and budget headers, but there is no backoff guidance for the general limits and no idempotency keys for writes were found (9). 99.95 per cent uptime SLA in the terms for the Enterprise package (10). The REST API is generally available and the MCP docs carry no beta label (10).)
- Security & auth, PostHog +19: Flagsmith 65 (OAuth for interactive MCP clients with Flagsmith as the authorisation server, Organisation API keys in the Authorization header that act as admin or with chosen RBAC roles, and OIDC trust relationships that swap a CI token for a short-lived one. Granular key roles need Scale-Up or Enterprise, so a Free key is all-powerful (25 of 30). RBAC roles can limit a key to reads, and change requests put a flag change through approval on Scale-Up and Enterprise. There is no read-only switch on the MCP server itself (14 of 20). No prompt-injection guidance; tools return names, descriptions and trait values written by people (3 of 15). Audit logs record every admin action and stream by webhook, on Scale-Up and Enterprise (11 of 15). The docs say Flagsmith has a SOC 2 Type 2 report available on request, the terms promise a yearly third-party penetration test, and SECURITY.md routes reports to support email. No security.txt, bug bounty or public advisory process was found (12 of 20). 25+14+3+11+12 = 65.); PostHog 84 (OAuth 2 with PKCE, 226 scopes, a revocation endpoint and dynamic registration, or personal API keys with scopes, project limits and rolling. A key can still be created with full access, and keys found in public GitHub repositories are rolled automatically (28). Read-only mode, filters by product area or tool, project pinning, and a typed confirmation for 18 admin actions (18). The MCP docs warn about prompt injection and tell users to review tool calls, and the CLI escapes informational responses. No further mitigation is documented for event and replay data that end users wrote (9). Activity logs with an API, MCP calls recorded with the caller's IP, and an admin view of every key with last use. Longer retention needs a platform package (12). security.txt valid to 30 August 2027, Bugcrowd disclosure programme paid in merchandise, public SOC 2 Type 2 report, annual penetration test and a public advisories page (17).)
- Schema & documentation, PostHog +14: Flagsmith 67 (openapi.yaml in the repository is OpenAPI 3.1 with 624 operations, and the MCP server builds its 54 tools from the operations tagged `mcp`, so every tool has a JSON Schema input (25). No llms.txt (404) and no Markdown served for agents on docs.flagsmith.com; the docs are Markdown only in the repository (0). Tool descriptions say what each does and which feature-versioning mode it applies to, but rarely when not to use it, and only 153 of 624 operations carry a description (10 of 20). 57 enums and required fields in the spec, with some free-form value fields (10 of 15). Docs carry curl examples, but only 16 operations document a 400 and 6 a 404 (7 of 15). A /api/v1 path, release-please changelog and dated release notes (15). 25+0+10+10+7+15 = 67.); PostHog 81 (OpenAPI 3.1 served without a login, 1,742 paths and 2,347 operations, and typed JSON Schema inputs on the MCP tools (25). llms.txt, and every docs page has a Markdown copy at the same address with .md (10). 1,487 of 2,347 operations (63 per cent) have a description. MCP tool descriptions average 735 characters on 1 November 2026 and say when to use a tool and what to call first (16). 1,243 enums across 4,792 schemas and a required scope on most operations (13). 706 examples in the spec. It documents 400 on 224 operations and 429 on 55, and the docs show the error shape with examples (9). Dated public changelog with RSS, but the spec version is fixed at 1.0.0 and the API has no versions (8).)
- Maintenance & community, PostHog +6: Flagsmith 83 (v2.290.0 was released on 5 November 2026 (30). 34 tagged releases between 8 August and 5 November (20). Commits land daily (60 since 8 August in the 60-commit clone), with a Discord server and support email. We couldn't read issue response times because GitHub's API refused us for its rate limit (15 of 25). Not in the official MCP registry, which returned no Flagsmith entry; official SDKs are current (8 of 15). Renovate updates, CI workflows for the API, frontend, docs and MCP, and a Trivy scan (10). 30+20+15+8+10 = 83.); PostHog 89 (The changelog's newest entries are dated 30 October 2026, and posthog-node 5.61.1 and the Python SDK's posthog-v7.81.1 came out the same day (30). 204 dated changelog entries since 3 August 2026 (20). Public changelog, community questions and in-app support. Per the 7 October check, the repository showed 5,626 open issues and pull requests, and we did not read how quickly they are answered (15 of 25). `io.github.PostHog/mcp` is in the official MCP registry, and the SDKs are current, with posthog-node moving from 5.55.0 to 5.61.1 between 7 and 30 October 2026 (15). 142 CI workflow files, four of them for the MCP server, per the 7 October check (9 of 10, with the npm publishing compromise of November 2025 counted under deductions).)
- Transparency & trust, PostHog +6: Flagsmith 77 (BSD-3-Clause for the core and the MCP server; the about page says most of the product is under that licence and some CI runs with private packages, so not every Cloud feature is in the open repository (25 of 30). The terms set Flagsmith as processor with 48-hour breach notice and EEA transfer rules, and the sub-processor list is dated 13 October 2025. The privacy policy dates from October 2023 and states no retention periods (16 of 30). The Gram-hosted MCP server was retired with a dated notice (30 June 2026), and three spec operations are marked deprecated, without a stated deprecation policy (10 of 20). The sub-processor list names providers and their countries (16 of 20). 25+16+10+16 = 67.); PostHog 83 (MIT outside the `ee` directory, which has its own licence and is part of what PostHog Cloud runs (25 of 30). Privacy policy, a self-serve DPA and the terms agree. The terms let PostHog use de-identified customer content to train its own models unless the customer opts out, and bar third parties from training on it. The privacy policy gives no retention periods, while the pricing page gives 1 year on the free plan and 7 on paid (22). No deprecation policy was found, and the query docs reserve the right to restrict export-like queries without notice. 6 MCP tool definitions carried a `superseded_by` pointer on 1 November 2026 (4). Sub-processor list updated 12 June 2026 with locations, 14 days' notice of changes, and data in Virginia or Germany (20).)