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SKILL.md
npx skills add apollographql/skills --skill apollo-federation
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.
npx skills add apollographql/skills --skill apollo-federation
Apollo Federation enables composing multiple GraphQL APIs (subgraphs) into a unified supergraph.
Every Federation 2 subgraph must opt-in via @link:
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
@linkversion is a floor, not the composition version — see Federation versions for the full explanation.
| 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 |
Detailed documentation for specific topics:
@link directive@shareable without ensuring all subgraphs return identical values for that field@key with single ID field for simple entity identificationrover supergraph compose to validate composition locallyrover subgraph check to validate against production supergraphtype Product @key(fields: "id") {
id: ID!
name: String!
price: Int
}# 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
}type Product @key(fields: "id") {
id: ID!
size: Int @external
weight: Int @external
shippingEstimate: String @requires(fields: "size weight")
}type Money @shareable {
amount: Int!
currency: String!
}type Product @key(fields: "id", resolvable: false) {
id: ID!
}