Every organization we talk to has more APIs than anyone can see at once, spread across teams, gateways, and repositories — which is exactly how the same capability gets built three times. The honest question, how reusable is what we already have?, goes unanswered because answering it usually means a project. So we built API Reusability to make it answerable in a browser tab: discover the evidence, inventory it as a portable index, and score it. Nothing leaves the page, and your keys stay in localStorage.
Try it → reusability.apicommons.org
Discover, Then Inventory
API Reusability pulls evidence of APIs from wherever they live: APIs.io catalog search with no key, code search across GitHub / GitLab / Bitbucket with your own token, and a HAR upload that synthesizes an evidence-based OpenAPI from real captured traffic — paths, parameters, headers, response schema. For gateways and wikis a browser can’t safely reach — AWS API Gateway, Kong, Tyk, Confluence — a tiny local helper CLI pulls the specs into a bundle you import. Everything is then indexed as OpenAPI into a single APIs.json 0.21 file: the durable, re-importable reusability index for your org.
Two Axes, Plus Duplication
Reusability is scored on two axes and a cross-API duplication check, rolled up by org / team / domain.
| Axis | Question | Weighted highest |
|---|---|---|
| A — OpenAPI design | How reusable is the interface? | schema reuse via components + $ref |
| B — APIs.json metadata | How discoverable & adoptable is it? | linked OpenAPI, docs, license, companion artifacts |
| Duplication | Is it already built elsewhere? | repeated paths & near-identical schemas → consolidation |
The composite is wA·design + wB·metadata + wD·(1 − duplication), graded A–F. The weights are tunable in Config → Scoring weights, and your org’s definition of reuse gets published on the Rubric tab rather than left undefined — this is your score, not ours.
Before, and After
Two things close the loop. An intent search — “what are you trying to build?” — surfaces reuse candidates before a team goes down the rabbit hole and builds from scratch. And a reuse ledger records when a team actually adopts an existing API, because the one number every API program struggles to produce is reuse actually happening.
API Reusability is one of the API Commons tools, and like the rest it is browser-first, portable, and open — an APIs.json index underneath, so what you build here travels. This is part of a series introducing the tools one at a time.