apollo-federation

name apollo-federation description Guide for authoring Apollo Federation subgraph schemas. Use this skill when: (1) creating new subgraph schemas for a federated supergraph, (2) defining or modifying entities with @key, (3) sharing types/fields across subgraphs with @shareable, (4) working with federation directives (@external, @requires, @provides, @override, @inaccessible), (5) troubleshooting composition errors, (6) any task involving federation schema design patterns. license MIT compatibility Works with any Federation 2.x compatible subgraph library (Apollo Server, GraphQL Yoga, etc.) metadata {"author":"apollographql","version":"1.0.2"} allowed-tools Bash(rover:*) Read Write Edit Glob Grep Apollo Federation Schema Authoring Apollo Federation enables composing multiple GraphQL APIs (subgraphs) into a unified supergraph. Federation 2 Schema Setup Every Federation 2 subgraph must opt-in via @link : extend schema @link ( url : "https://specs.apollo.dev/federation/v2.12" , import : [ "@key" , "@shareable" , "@external" , "@requires" , "@provides" ] ) Import only the directives your subgraph uses. The version shown ( v2.12 ) is illustrative — check the Federation changelog for currently supported versions before copying it verbatim. A subgraph's @link version is a floor, not the composition version — see Federation versions for the full explanation. Core Directives Quick Reference Directive Purpose Example @key Define entity with unique key type Product @key(fields: "id") @shareable Allow multiple subgraphs to resolve field type Position @shareable { x: Int! } @external Reference field from another subgraph weight: Int @external @requires Computed field depending on external fields shippingCost: Int @requires(fields: "weight") @provides Conditionally resolve external field @provides(fields: "name") @override Migrate field to this subgraph @override(from: "Products") @inaccessible Hide from API schema internalId: ID! @inaccessible @interfaceObject Add fields to entity interface type Media @interfaceObject Reference Files Detailed documentation for specific topics: Directives - All federation directives with syntax, examples, and rules Schema Patterns - Multi-subgraph patterns and recipes Composition - Composition rules, error codes, and debugging Key Patterns Entity Definition type Product @key ( fields : "id" ) { id : ID ! name : String ! price : Int } Entity Contributions Across Subgraphs # Products subgraph type Product @key ( fields : "id" ) { id : ID ! name : String ! price : Int } # Reviews subgraph type Product @key ( fields : "id" ) { id : ID ! reviews : [ Review ! ] ! averageRating : Float } Computed Fields with @requires type Product @key ( fields : "id" ) { id : ID ! size : Int @external weight : Int @external shippingEstimate : String @requires ( fields : "size weight" ) } Value Types with @shareable type Money @shareable { amount : Int ! currency : String ! } Entity Stub (Reference Without Contributing) type Product @key ( fields : "id" , resolvable : false ) { id : ID ! } Ground Rules ALWAYS use Federation 2.x syntax with @link directive ALWAYS import only the directives your subgraph uses NEVER use @shareable without ensuring all subgraphs return identical values for that field PREFER @key with single ID field for simple entity identification USE rover supergraph compose to validate composition locally USE rover subgraph check to validate against production supergraph