The Open-Source tag at apis.io/tags/open-source/ is carried by 1,087 providers but only 210 APIs. Its aggregate composite is 29.9, which places the tag in the niche band.
1,087 providers and 210 APIs. That five-to-one inversion is the finding, and it is the opposite shape of every other large tag in the catalog.
Company attribute, not API attribute
Compare with the Authentication tag covered this week: 1,338 providers and 1,207 APIs — roughly one-to-one, because authentication is something an API does.
Open-source is something a company is. It attaches to the provider — the software is on GitHub, the licence is permissive, the community is real — and then mostly stops. Only 210 APIs inherit it, because the hosted API a company sells is frequently the one thing that is not open.
That is not hypocrisy; it is the business model. The open-core pattern is: give away the software, sell the hosted service. The software’s licence has no bearing on how well the hosted API is described.
Why the composite is low
29.9 is a niche-band score, and there are two contributing effects.
First, the tag pulls in a long tail of small open-source projects that expose an HTTP interface without a formal API program. A well-run project with a great README and no OpenAPI definition scores poorly on a rubric that measures machine-readable description, and it should — a README is not a specification.
Second, open-source culture historically treated the code as the documentation. If you can read the handler, you know the contract. That is true for contributors and useless for anyone integrating over the network, and it is exactly the gap the Kin Score measures.
The counterexamples matter
The tag average understates its best members badly. This week’s profiles include several companies whose products are open-source or open-core and which score in the exemplar band on description quality — Grafana, Kong, and JFrog all sit far above 29.9.
Those companies made a deliberate move: treat the hosted API as a product with its own specification, rather than as an artifact that falls out of the codebase. The tag’s low average is a statement about the long tail, not about open source as a practice.
Takeaway
1,087 providers carry the open-source tag; only 210 APIs do. Open-source is a company property that rarely propagates to API description quality, and a repository is not a specification. The projects that closed that gap did it on purpose.
Browse the tag at apis.io/tags/open-source/.