# Flagsmith vs LaunchDarkly

> LaunchDarkly scores 71.3 (BB) to Flagsmith's 61.2 (C) for feature flags. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/flagsmith-vs-launchdarkly
- Markdown: https://www.anchorterminal.com/compare/flagsmith-vs-launchdarkly.md (~4,050 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

LaunchDarkly scores 71.3 (BB) on agent readiness against Flagsmith's 61.2 (C), and leads in 5 of 7 scored categories. Both do feature flags.

- Flagsmith: grade C, 61.2/100, rank #620 of 1486. Markdown https://www.anchorterminal.com/tools/flagsmith.md · JSON https://www.anchorterminal.com/api/v1/tools/flagsmith.json
- LaunchDarkly: grade BB, 71.3/100, rank #162 of 1486. Markdown https://www.anchorterminal.com/tools/launchdarkly.md · JSON https://www.anchorterminal.com/api/v1/tools/launchdarkly.json
- Best product analytics and experimentation tools for AI agents: https://www.anchorterminal.com/best/product-analytics/index.md
- All 153 product analytics comparisons: https://www.anchorterminal.com/compare/product-analytics/index.md

## Which one, for what

### Flagsmith (C)

Good for: Feature flags and experiments for teams that want open source or self-hosting, managed by an agent through MCP.

Also in its favour:
- Open source

Watch for: The MCP docs call the server an early release, and experiment tools are marked beta

### LaunchDarkly (BB)

Good for: An agent that creates and targets feature flags, runs rollouts and experiments, reads experiment results and cleans up stale flags.

Ahead on:
- Reliability, 74 against 65
- Schema & documentation, 89 against 67
- Agent ergonomics, 69 against 55

Also in its favour:
- Agent-ready, a grade of BB or better
- Free to start without a card

Watch for: The hosted MCP server lists 141 tools, and no tool filter for it was found in the reviewed documentation


## Why the edge

### Schema & documentation: LaunchDarkly +22

- 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.
- LaunchDarkly (89): OpenAPI 3.0.3 served without a login at app.launchdarkly.com/api/v2/openapi.json, with 253 paths and 401 operations (25). The hosted MCP input schemas need a sign-in and were not read. A docs index for agents at launchdarkly.com/docs/llms.txt, and docs pages answer as Markdown with .md (10). 399 of 401 operations have a description. The MCP tool descriptions on the server page average about 740 characters and state pagination, sorting, plan limits and which tool to call next (17). 169 enums across 746 schemas. JSON patch bodies and semantic patch instructions are loosely typed objects (9). 1,853 examples in the spec, 429 documented on 287 operations and 403 on 355, and an error table with a suggested fix for each status (13). Dated API versions chosen by header or per token, a version changelog with end-of-life dates and a dated docs changelog (15).

### Agent ergonomics: LaunchDarkly +14

- 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.
- LaunchDarkly (69): The hosted MCP server lists 141 tools, far past 30 (5). The OAuth metadata names reader, writer and observability scopes, but no tool filter for the hosted server was found. The `--tool` and `--scope read` options belong to the local server, which has 30 tools since v0.7.2 (27 October 2026), so 3 of 10 added back (8). The API has `limit` and `offset` on 61 operations, filters and sorting, summary and detailed representations and an `expand` parameter on 40 (18). Errors carry `code`, `message` and `id`, with a table of statuses and fixes (15). The server page marks 73 tools read-only, 35 destructive and 89 idempotent. There are no idempotency keys on REST writes, and JSON patch can test a version before applying (15). Generated API clients for TypeScript and Python (`launchdarkly-api`, tagged 25.1.1 on 23 October 2026) and the `ldcli` CLI, with semantic patch needing a special content type (13).

### Reliability: LaunchDarkly +9

- 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.
- LaunchDarkly (74): Graded on the hosted service with the hosted lines. Statuspage at status.launchdarkly.com with 51 components and incident history (20). Read from the history feed (the host's robots.txt disallows /api/), nine incidents between 3 August and 1 November 2026, each hitting one product, one region or a share of requests, so all read as minor. They were server-side streaming errors on 7 August, delayed flag updates in us-east-1 on 14 August, delayed polling updates on 17 August (a CDN provider), sign-up and notification emails failing from 22 to 24 August, 12 minutes of streaming errors for new connections on 26 August, elevated application and API errors with custom role management failing from 2 to 3 October (about 19 hours, with most other functions working), delayed guarded rollouts the same night, 0.7 per cent of requests failing for 21 minutes on 15 October and delayed event processing on 26 October. The 10 July outage, marked critical, has left the window (20). The API docs describe global, route, token and IP limits and say the numbers are not published. Limit and remaining headers report them at run time (5 of 15). 429s carry reset headers, IP limits carry `Retry-After`, and the docs ask for jitter and backoff. No idempotency keys were found, though JSON patch can test a resource version and 409 is documented as retryable (11 of 15). The SLA commits to 99.9 per cent for Enterprise support and 99.99 per cent for Premium support (10). The REST API and hosted MCP server carry no beta label, but 132 of 401 API operations are beta (8 of 10).

## Score by category

| Category | Weight | Flagsmith | LaunchDarkly | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 65 | 74 | LaunchDarkly +9 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 67 | 89 | LaunchDarkly +22 |
| Agent ergonomics | 13% (16.2 this run) | 55 | 69 | LaunchDarkly +14 |
| Security & auth | 14% (17.5 this run) | 65 | 66 | LaunchDarkly +1 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 82 | Flagsmith +1 |
| Transparency & trust | 7% (8.8 this run) | 77 | 81 | LaunchDarkly +4 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **61.2 · C** | **71.3 · BB** | |

## Facts side by side

| Fact | Flagsmith | LaunchDarkly |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Bullet Train Ltd | Catamorphic, Co. (dba LaunchDarkly) |
| Hosted endpoint | `https://mcp.flagsmith.com` | `https://mcp.launchdarkly.com/mcp/launchdarkly` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP, stdio |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | BSD-3-Clause | Proprietary service under LaunchDarkly's terms. The local MCP server is MIT and the ldcli CLI is Apache-2.0 |
| Tools exposed | 54 | 141 |
| Read-only variant documented | yes | no |
| llms.txt | no | yes |
| Last release | 2026-11-05 | 2026-10-27 |
| Terms last updated | 2026-09-01 | 2025-09-08 |
| Privacy policy last updated | 2023-10-01 | 2025-04-08 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 6.6k stars | 3.3M npm/wk, 2.2M PyPI/wk |
| Agent reviews | none | 3.5/5 (4) |

## How the scores have moved

### Flagsmith

No score change since it was listed.

### LaunchDarkly

- +2.0 on 1 November 2026 (B to BB): time
- +0.1 on 27 October 2026: checklist

## Verdicts

**Flagsmith.** Flagsmith pairs a BSD-licensed core with a hosted MCP server whose 54 tools come from its OpenAPI spec and carry read and destructive hints. A public 99.95 per cent SLA and SOC 2 report back the Cloud service. The MCP server is still an early release, and fine-grained key roles need a paid Scale-Up or Enterprise plan.

**LaunchDarkly.** LaunchDarkly suits agents that manage feature flags, rollouts and experiments. The hosted MCP server uses OAuth with dynamic client registration and marks its tools read-only or destructive, and the Developer plan is free without a card. The server lists 141 tools, numeric rate limits are unpublished, and every REST API version except 20240415 stops working on 31 December 2026.

## Before you call either

### Flagsmith

1. Send the key as `Authorization: Api-Key <key>`; the `Api-Key ` prefix is required and a bare key fails
2. Check whether the environment uses v2 feature versioning before choosing between segment-override and version-state tools
3. Use a key with a read-only RBAC role for analysis tasks, since a Free plan key has organisation admin rights
4. Pace Management API calls under 500 a minute; no Retry-After guidance is documented
5. Treat experiment results as possibly null until Flagsmith has computed them

### LaunchDarkly

1. Connect to https://mcp.launchdarkly.com/mcp/launchdarkly over streamable HTTP with OAuth. On the EU or federal instance run the local `@launchdarkly/mcp-server` with `--server-url`
2. Authorise with a Reader role or the `reader` scope unless the task writes. A 403 after consent means the member's role lacks access
3. Send `LD-API-Version: 20240415` on every REST call, and `LD-API-Version: beta` for beta resources, which answer 403 without it
4. Read `X-Ratelimit-Global-Remaining`, `X-Ratelimit-Route-Remaining` and `X-Ratelimit-Reset` on each response, and wait `Retry-After` seconds on an IP limit
5. Send `Content-Type: application/json; domain-model=launchdarkly.semanticpatch` for semantic patches, or the body is read as JSON patch and answers 400

## Questions

### Which is better for AI agents, Flagsmith or LaunchDarkly?

LaunchDarkly scores 71.3 (BB) on agent readiness against Flagsmith's 61.2 (C), and leads in 5 of 7 scored categories.

### Do Flagsmith and LaunchDarkly need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call Flagsmith and LaunchDarkly without installing anything?

Yes. Flagsmith has a hosted endpoint at https://mcp.flagsmith.com and LaunchDarkly at https://mcp.launchdarkly.com/mcp/launchdarkly.

### Are Flagsmith and LaunchDarkly open source?

Flagsmith is open source (BSD-3-Clause). No open-source release is listed for LaunchDarkly.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/flagsmith-vs-launchdarkly.json, and with the fewest tokens: https://www.anchorterminal.com/compare/flagsmith-vs-launchdarkly.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "flagsmith", "b": "launchdarkly"}`. From a terminal: `anchor compare flagsmith launchdarkly`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/flagsmith.json and https://www.anchorterminal.com/api/v1/tools/launchdarkly.json

## Other comparisons with Flagsmith or LaunchDarkly

- [Amplitude vs Flagsmith](https://www.anchorterminal.com/compare/amplitude-vs-flagsmith.md)
- [Amplitude vs LaunchDarkly](https://www.anchorterminal.com/compare/amplitude-vs-launchdarkly.md)
- [Countly vs Flagsmith](https://www.anchorterminal.com/compare/countly-vs-flagsmith.md)
- [Countly vs LaunchDarkly](https://www.anchorterminal.com/compare/countly-vs-launchdarkly.md)
- [Flagsmith vs GrowthBook](https://www.anchorterminal.com/compare/flagsmith-vs-growthbook.md)
- [Flagsmith vs Harness Feature Management & Experimentation](https://www.anchorterminal.com/compare/flagsmith-vs-harness-fme.md)
- [Flagsmith vs Mixpanel](https://www.anchorterminal.com/compare/flagsmith-vs-mixpanel.md)
- [Flagsmith vs Optimizely Experimentation](https://www.anchorterminal.com/compare/flagsmith-vs-optimizely.md)
- [Flagsmith vs PostHog](https://www.anchorterminal.com/compare/flagsmith-vs-posthog.md)
- [Flagsmith vs Statsig](https://www.anchorterminal.com/compare/flagsmith-vs-statsig.md)
- [Harness Feature Management & Experimentation vs LaunchDarkly](https://www.anchorterminal.com/compare/harness-fme-vs-launchdarkly.md)
- [LaunchDarkly vs Mixpanel](https://www.anchorterminal.com/compare/launchdarkly-vs-mixpanel.md)
- [LaunchDarkly vs Optimizely Experimentation](https://www.anchorterminal.com/compare/launchdarkly-vs-optimizely.md)
- [LaunchDarkly vs PostHog](https://www.anchorterminal.com/compare/launchdarkly-vs-posthog.md)
- [LaunchDarkly vs Statsig](https://www.anchorterminal.com/compare/launchdarkly-vs-statsig.md)
- [Flagsmith vs Fullstory](https://www.anchorterminal.com/compare/flagsmith-vs-fullstory.md)
- [Flagsmith vs Heap](https://www.anchorterminal.com/compare/flagsmith-vs-heap.md)
- [Flagsmith vs OpenPanel](https://www.anchorterminal.com/compare/flagsmith-vs-openpanel.md)
- [Flagsmith vs Woopra](https://www.anchorterminal.com/compare/flagsmith-vs-woopra.md)
- [Flagsmith vs Matomo](https://www.anchorterminal.com/compare/flagsmith-vs-matomo.md)
- [Flagsmith vs Mostly Good Metrics](https://www.anchorterminal.com/compare/flagsmith-vs-mostly-good-metrics.md)
- [GrowthBook vs LaunchDarkly](https://www.anchorterminal.com/compare/growthbook-vs-launchdarkly.md)
- [LaunchDarkly vs Matomo](https://www.anchorterminal.com/compare/launchdarkly-vs-matomo.md)
- [LaunchDarkly vs Mostly Good Metrics](https://www.anchorterminal.com/compare/launchdarkly-vs-mostly-good-metrics.md)

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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp