API development and testing covers different jobs, from exercising requests and gateways to emulating cloud services and routing model APIs. This October 2026 snapshot uses the supplied ToolVitals records to show which open or source-visible tools score strongest for the use case.
The ranking includes open/source-visible tools and orders them by ToolVitals score descending, with health and shipping used to break equal composite scores. GitHub stars are context only and do not determine rank.
Rankings
| Rank | Tool | Openness | License | Health | Shipping | GitHub Stars | Score | Status |
|---|---|---|---|---|---|---|---|---|
| 1 | LiteLLM | OSI-approved OSS | MIT | 98 | 99 | 60008 | 99 | 🟢 Excellent |
| 2 | Bifrost | OSI-approved OSS | Apache-2.0 | 98 | 98 | 8485 | 98 | 🟢 Excellent |
| 3 | Ministack | OSI-approved OSS | MIT | 97 | 97 | 4758 | 97 | 🟢 Excellent |
| 4 | Bruno | OSI-approved OSS | MIT | 97 | 96 | 47301 | 97 | 🟢 Excellent |
| 5 | Scalar | OSI-approved OSS | MIT | 97 | 96 | 16217 | 97 | 🟢 Excellent |
| 6 | new-api | OSI-approved OSS | AGPL-3.0 | 97 | 96 | 49150 | 97 | 🟢 Excellent |
| 7 | WunderGraph | OSI-approved OSS | Apache-2.0 | 97 | 96 | 1272 | 96 | 🟢 Excellent |
| 8 | AxonHub | OSI-approved OSS | Apache-2.0 | 97 | 95 | 5328 | 96 | 🟢 Excellent |
| 9 | MCP Context Forge | OSI-approved OSS | Apache-2.0 | 97 | 95 | 4555 | 96 | 🟢 Excellent |
| 10 | Traefik | OSI-approved OSS | MIT | 97 | 95 | 65024 | 96 | 🟢 Excellent |
| 11 | Unkey | OSI-approved OSS | AGPL-3.0 | 96 | 96 | 5455 | 96 | 🟢 Excellent |
| 12 | Insomnia | OSI-approved OSS | Apache-2.0 | 96 | 95 | 40037 | 96 | 🟢 Excellent |
| 13 | Keploy | OSI-approved OSS | Apache-2.0 | 96 | 95 | 18522 | 96 | 🟢 Excellent |
| 14 | Kuadrant MCP Gateway | OSI-approved OSS | Apache-2.0 | 96 | 95 | 104 | 96 | 🟢 Excellent |
| 15 | Specmatic | OSI-approved OSS | MIT | 96 | 95 | 396 | 96 | 🟢 Excellent |
| 16 | kgateway | OSI-approved OSS | Apache-2.0 | 96 | 95 | 5695 | 96 | 🟢 Excellent |
| 17 | OpenAPI Generator | OSI-approved OSS | Apache-2.0 | 96 | 94 | 26771 | 95 | 🟢 Excellent |
| 18 | FakeCloud | OSI-approved OSS | AGPL-3.0 | 95 | 96 | 731 | 95 | 🟢 Excellent |
| 19 | Inference Gateway | OSI-approved OSS | Apache-2.0 | 95 | 95 | 214 | 95 | 🟢 Excellent |
| 20 | Apache APISIX | OSI-approved OSS | Apache-2.0 | 95 | 94 | 17187 | 95 | 🟢 Excellent |
| 21 | Higress | OSI-approved OSS | Apache-2.0 | 95 | 93 | 9484 | 94 | 🟢 Excellent |
| 22 | testcontainers-go | OSI-approved OSS | MIT | 95 | 92 | 4992 | 94 | 🟢 Excellent |
| 23 | Membrane API Gateway | OSI-approved OSS | Apache-2.0 | 94 | 94 | 644 | 94 | 🟢 Excellent |
| 24 | PostgREST | OSI-approved OSS | MIT | 94 | 94 | 27692 | 94 | 🟢 Excellent |
| 25 | Karate | OSI-approved OSS | MIT | 93 | 94 | 8972 | 94 | 🟢 Excellent |
| 26 | Microcks | OSI-approved OSS | Apache-2.0 | 94 | 91 | 2051 | 92 | 🟢 Excellent |
| 27 | Kumo | OSI-approved OSS | MIT | 92 | 91 | 1492 | 92 | 🟢 Excellent |
| 28 | Gravitee | OSI-approved OSS | Apache-2.0 | 93 | 88 | 458 | 91 | 🟢 Excellent |
| 29 | Hurl | OSI-approved OSS | Apache-2.0 | 92 | 88 | 19229 | 91 | 🟢 Excellent |
| 30 | Tyk | OSI-approved OSS | AGPL-3.0 | 92 | 87 | 10840 | 90 | 🟢 Excellent |
| 31 | HttpArena | OSI-approved OSS | MIT | 91 | 87 | 121 | 90 | 🟢 Excellent |
| 32 | Emissary | OSI-approved OSS | Apache-2.0 | 91 | 88 | 4525 | 89 | 🟢 Excellent |
| 33 | API Dash | OSI-approved OSS | Apache-2.0 | 89 | 85 | 2915 | 87 | 🟢 Excellent |
| 34 | Hasura | OSI-approved OSS | Apache-2.0 | 88 | 83 | 32130 | 86 | 🟢 Excellent |
| 35 | KrakenD | OSI-approved OSS | Apache-2.0 | 88 | 83 | 2690 | 86 | 🟢 Excellent |
| 36 | MCP Assert | OSI-approved OSS | MIT | 84 | 88 | 24 | 86 | 🟢 Excellent |
| 37 | OkHttp | OSI-approved OSS | Apache-2.0 | 88 | 79 | 47082 | 85 | 🟢 Excellent |
| 38 | GhostPour | OSI-approved OSS | MIT | 84 | 86 | 5 | 85 | 🟢 Excellent |
| 39 | Tailcall | OSI-approved OSS | Apache-2.0 | 85 | 79 | 1443 | 83 | 🟢 Excellent |
| 40 | Hoppscotch | OSI-approved OSS | MIT | 85 | 74 | 80557 | 81 | 🟢 Excellent |
| 41 | Requesto | OSI-approved OSS | MIT | 79 | 81 | 7 | 80 | 🟢 Excellent |
| 42 | tRPC | OSI-approved OSS | MIT | 83 | 72 | 40679 | 79 | 🟢 Good |
| 43 | pREST | OSI-approved OSS | MIT | 81 | 69 | 4617 | 76 | 🟢 Good |
| 44 | mitmproxy | OSI-approved OSS | MIT | 77 | 57 | 45212 | 69 | 🟢 Good |
| 45 | Kong | OSI-approved OSS | Apache-2.0 | 72 | 53 | 44228 | 64 | 🟢 Good |
| 46 | Apache JMeter | OSI-approved OSS | Apache-2.0 | 71 | 50 | 9550 | 63 | 🟢 Good |
| 47 | Restfox | OSI-approved OSS | MIT | 68 | 56 | 2765 | 63 | 🟢 Good |
| 48 | Fusio | OSI-approved OSS | Apache-2.0 | 67 | 58 | 2118 | 63 | 🟢 Good |
| 49 | Webhook.site | OSI-approved OSS | MIT | 64 | 43 | 6766 | 56 | 🟡 Fair |
| 50 | Yasumu | OSI-approved OSS | AGPL-3.0 | 53 | 42 | 46 | 48 | 🟡 Fair |
Top 3 Highlights
LiteLLM ranks first with a ToolVitals score of 99, a health score of 98, and a shipping score of 99. It is listed as OSI-approved OSS under the MIT license. The supplied description makes it a broad choice for AI API work: a Python SDK and Proxy Server (AI Gateway) for calling 100+ LLM APIs in OpenAI or native format, with cost tracking, guardrails, loadbalancing, and logging.
Bifrost ranks second with a ToolVitals score of 98, health of 98, and shipping of 98. It is listed as OSI-approved OSS under the Apache-2.0 license. Its supplied description focuses on gateway operations, including an adaptive load balancer, cluster mode, guardrails, support for 1000+ models, and stated <100 µs overhead at 5k RPS.
Ministack ranks third with a ToolVitals score, health score, and shipping score of 97. It is listed as OSI-approved OSS under the MIT license. The supplied description is focused: Ministack is a free, open-source local AWS emulator, making it the most directly targeted of the top three for local AWS-oriented API development and testing.
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