APIs.io is the search engine over the catalog. It indexes API providers and their APIs along with everything published around them — OpenAPI definitions, AsyncAPI, JSON Schema, MCP servers, agent skills, collections, plans and rate limits, security schemes, scopes, terms, and the rest.
It grew directly out of APIs.json, the discovery format I created: every provider in the network has an apis.yml describing what they publish and where it lives, and APIs.io is what you get when you index all of them and make the result searchable.
You can search it as a human, browse by industry, region, tag, use case, or rating band, and compare providers head to head. There is also an MCP server, because agents are now a legitimate consumer of exactly this kind of index — a machine that needs to find a capability, evaluate whether it is usable, and see the terms before calling it.
Discovery is free. The ratings depth, the synthesis, and the demand-side data are the paid layer.
