# Flagsmith vs Mostly Good Metrics

> Flagsmith scores 61.2 (C) to Mostly Good Metrics's 41.7 (E) for feature flags and experiments. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/flagsmith-vs-mostly-good-metrics
- Markdown: https://www.anchorterminal.com/compare/flagsmith-vs-mostly-good-metrics.md (~4,750 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

Flagsmith scores 61.2 (C) on agent readiness against Mostly Good Metrics's 41.7 (E), and leads in every scored category. Both do feature flags and experiments.

- Flagsmith: grade C, 61.2/100, rank #623 of 1510. Markdown https://www.anchorterminal.com/tools/flagsmith.md · JSON https://www.anchorterminal.com/api/v1/tools/flagsmith.json
- Mostly Good Metrics: grade E, 41.7/100, rank #1295 of 1510. Markdown https://www.anchorterminal.com/tools/mostly-good-metrics.md · JSON https://www.anchorterminal.com/api/v1/tools/mostly-good-metrics.json
- Best product analytics and experimentation tools for AI agents: https://www.anchorterminal.com/best/product-analytics/index.md
- All 170 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.

Ahead on:
- Reliability, 65 against 29
- Schema & documentation, 67 against 49
- Agent ergonomics, 55 against 49
- Security & auth, 65 against 33
- Payments & pricing, 40 against 30
- Maintenance & community, 83 against 74
- Transparency & trust, 77 against 45

Also in its favour:
- Runs on your own machine
- Open source

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

### Mostly Good Metrics (E)

Good for: Indie and small-team apps that want simple funnels and retention an agent can query.

Also in its favour:
- Free to start without a card

Watch for: Public beta run by one developer, with no named legal entity in the terms


## Why the edge

### Reliability: Flagsmith +36

- 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.
- Mostly Good Metrics (29): Graded on the hosted service with the hosted lines. No status page was found (0) and no incident history could be read (5). Ingestion limits are documented per plan (1,000 to 100,000 events a minute and 10,000 to 1,000,000 an hour), but no limit for MCP or query calls was found (12 of 15). 429 with Retry-After in the header and body, and the SDKs queue events and back off. No idempotency or safe-retry guidance for writes (12 of 15). No SLA (0). The press kit calls the product a public beta (0). 0+5+12+12+0+0 = 29.

### Security & auth: Flagsmith +32

- 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.
- Mostly Good Metrics (33): OAuth 2.0 with PKCE, dynamic client registration and a revocation endpoint for MCP and the CLI; project ingest keys in a Bearer header that can be pinned to origins or app IDs. The only tool scope advertised is mcp:tools, so a connection gets every tool the user can use (24 of 30). Restricted keys and a confirmation step for unrestricted keys in the CLI; no read-only MCP mode or approval for deletes was found (6 of 20). Event properties come from apps and end users and reach the agent, and no prompt-injection guidance was found (3 of 15). No audit log was found (0). No security.txt, disclosure policy or certification was found (0). 24+6+3+0+0 = 33.

### Transparency & trust: Flagsmith +32

- 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.
- Mostly Good Metrics (45): The service is closed; the SDKs and CLI are MIT. Terms of December 2025 with no legal entity named (18 of 30). The privacy policy and terms agree on raw-event retention for the subscription's life and deletion within 14 days of account deletion; the about page says data is not used to train models. No DPA was found (18 of 30). The legacy X-MGM-Key header is still supported, and no deprecation policy was found (3 of 20). The terms name eight sub-processors with their purpose, without data locations (12 of 20). 18+18+3+12 = 51.

### Schema & documentation: Flagsmith +18

- 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.
- Mostly Good Metrics (49): No OpenAPI file was found. The docs say every MCP tool describes its own parameters, and the query definition object is documented in full; we didn't open an MCP session to read the schemas (12 of 25). No llms.txt (404) and no Markdown pages served for agents (0). Each tool area is documented with examples, and the docs say when to use query_metrics instead of repeated execute_query calls (10 of 20). The query definition lists metrics, dimensions, date ranges and filter operators (9 of 15). The ingestion API documents its error body and status codes, and query_metrics reports per-item errors (11 of 15). /v1 and /api/v2 paths and dated SDK tags, but no product changelog (7 of 15). 12+0+10+9+11+7 = 49.

### Payments & pricing: Flagsmith +10

- Flagsmith (40): No x402, MPP or L402 (0). Plan prices and the per-million overage are public without login, though the page gives two overage rates for Start-Up ($50 per million and $7 per 100,000) (20). A $0 Free plan with 50,000 requests a month and a free BSD-3-Clause self-hosted edition. The pricing page doesn't say whether a card is needed, but the Free plan has no charge and the self-hosted edition needs no account (20). A person signs up in a browser, then approves OAuth or creates a key (0). 0+20+20+0 = 40.
- Mostly Good Metrics (30): No x402, MPP or L402 (0). Plan prices with event allowances are on the home page; no per-event price (10). Free plan with no card, stated on the home and about pages (20). Signup and OAuth approval happen in a browser (0). 0+10+20+0 = 30.

### Maintenance & community: Flagsmith +9

- 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.
- Mostly Good Metrics (74): CLI v0.1.4 was tagged on 16 October 2026 (30). The JavaScript SDK released 0.12.0, 0.13.0 and 0.13.1 between 5 September and 2 October, and the Swift SDK 1.0.0 and 1.0.1 on 2 October (20). A closed service with no public changelog, support by email and GitHub repositories for the SDKs; issue activity wasn't read because the GitHub API refused us for its rate limit (6 of 25). Not in the official MCP registry; official SDKs in five languages are current (10 of 15). CI workflows on the SDK and CLI repositories (8 of 10). 30+20+6+10+8 = 74.

## Score by category

| Category | Weight | Flagsmith | Mostly Good Metrics | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 65 | 29 | Flagsmith +36 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 67 | 49 | Flagsmith +18 |
| Agent ergonomics | 13% (16.2 this run) | 55 | 49 | Flagsmith +6 |
| Security & auth | 14% (17.5 this run) | 65 | 33 | Flagsmith +32 |
| Payments & pricing | 10% (12.5 this run) | 40 | 30 | Flagsmith +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 74 | Flagsmith +9 |
| Transparency & trust | 7% (8.8 this run) | 77 | 45 | Flagsmith +32 |
| Negative events | ≤15 | -2 | 0 | |
| **Total** | | **61.2 · C** | **41.7 · E** | |

## Facts side by side

| Fact | Flagsmith | Mostly Good Metrics |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Bullet Train Ltd | Mostly Good Metrics |
| Hosted endpoint | `https://mcp.flagsmith.com` | `https://app.mostlygoodmetrics.com/mcp` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | BSD-3-Clause | none |
| Tools exposed | 54 | 53 |
| Read-only variant documented | yes | no |
| llms.txt | no | no |
| Last release | 2026-11-05 | 2026-10-16 |
| Terms last updated | 2026-09-01 | 2025-12-01 |
| Privacy policy last updated | 2023-10-01 | 2025-12-01 |
| 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 | not found in the text |
| 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 | 81 npm/wk |

## 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.

**Mostly Good Metrics.** Mostly Good Metrics lets an agent run ad-hoc funnels, retention and up to ten metric queries per call through a hosted MCP server with OAuth, at prices from $0. It is a public beta built by one developer, with no status page, no named legal entity and no security policy found.

## 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

### Mostly Good Metrics

1. Use query_metrics for several aggregate questions instead of repeated execute_query calls
2. Pass inline definitions to execute_funnel and execute_retention rather than creating saved objects
3. Confirm with the user before delete, revoke_api_key or stop_experiment calls, since the server doesn't ask
4. Start a fresh agent session after connecting, since a running client may not reload the tool list
5. On 429 from ingestion, wait for Retry-After before resending events

## Questions

### Which is better for AI agents, Flagsmith or Mostly Good Metrics?

Flagsmith scores 61.2 (C) on agent readiness against Mostly Good Metrics's 41.7 (E), and leads in every scored category.

### Do Flagsmith and Mostly Good Metrics need an API key?

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

### Can an agent call Flagsmith and Mostly Good Metrics without installing anything?

Yes. Flagsmith has a hosted endpoint at https://mcp.flagsmith.com and Mostly Good Metrics at https://app.mostlygoodmetrics.com/mcp.

### Are Flagsmith and Mostly Good Metrics open source?

Flagsmith is open source (BSD-3-Clause). No open-source release is listed for Mostly Good Metrics.


## For agents

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

## Other comparisons with Flagsmith or Mostly Good Metrics

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