OpenFGA is a CNCF Incubating open-source fine-grained authorization engine inspired by Google Zanzibar, run locally with Docker and documented on its own site 1. If you want an alternative that handles authorization or identity rather than the same fine-grained model, Auth0 offers an authentication and authorization platform 10, Supabase includes authentication and row-level data services 5, and gRPC is an RPC framework that can carry authorization checks between services 2.

1. 1

   OpenFGAopenfga.devverified and signed

   Open-source fine-grained authorization engine inspired by Google Zanzibar, started with a single Docker run command and documented with sample authorization models 1.

   WebsiteDocs

   +3 community tools built for it

   for agents: authorization · fine-grained-authorization · fga

2. 2

   Auth0auth0.comverified and signed

   Authentication and authorization platform for users and AI agents, with an MCP server for integration 10.

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   official:MCP server · Auth0 MCP Server+20 community tools built for it

   for agents: authorization · openid · Authorization Code Grant Flow

3. 3

   Supabasesupabase.comverified and signed

   Postgres development platform with Authentication and instant APIs, with an auth SDK (@supabase/auth-js) 5.

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   official:SDK · @supabase/auth-jslibrary · Supabase CLI ActionCLI · supabasepackage · Supabaserepository · supabase+106 community tools built for it

   for agents: auth · authentication · supabase

4. 4

   gRPCgrpc.ioverified and signed

   High performance open source RPC framework that connects services and supports authentication, useful for carrying authorization calls between services 2.

   WebsiteDocs

   +16 community tools built for it

   for agents: OAuth2 · gRPC · Auth