apollo-federation

★ 91

by apollographql · part of apollographql/skills

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.

🔥🔥🔥✓ VerifiedFreeQuick setup

#git

🔌 This skill ships inside the Apollo GraphQL Skills plugin — install the plugin and you also get an MCP server.

This is the playbook your agent receives when the skill activates — you don't need to read it to use the skill, but it's here to audit before installing.

Apollo Federation Schema Authoring

Apollo Federation enables composing multiple GraphQL APIs (subgraphs) into a unified supergraph.

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

Copy & paste — that's it

npx skills add apollographql/skills --skill "apollo-federation" --full-depth

Run this in your project — your agent picks the skill up automatically.

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.