Mercurius

High-performance GraphQL server for Fastify with Just-In-Time compilation via graphql-jit, automatic query caching, N+1 prevention via dataloader integration, federation support, subscription via WebSocket, batched query support, and GraphQL Playground integration.

Mercurius publishes 1 API on the APIs.io network. Tagged areas include GraphQL, Fastify, Node.js, Federation, and WebSocket.

Mercurius’ developer surface includes documentation and 8 more developer resources.

🌐 Visit website 📡 Source on GitHub

19.2/100 emerging ▬ flat Agent 16/100 agent aware saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

1 APIs

GraphQLFastifyNode.js Federation WebSocket Open-Source

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 19.2/100 · emerging

Contract Quality 9.1 / 25

Developer Ergonomics 1.9 / 20

Access Clarity 0.0 / 20

Operational Transparency 0.7 / 13

Contract Governance 0.0 / 12

Discoverability 7.6 / 10

Agent readiness — 16/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/mercurius: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 1

Individual APIs this provider publishes, each with its own machine-readable definition.

Mercurius API

GraphQL adapter for Fastify enabling high-performance GraphQL servers and gateways with JIT compilation, query caching, subscriptions, and federation.

GraphQL 1

GraphQL schemas published by this provider.

Mercurius GraphQL

Mercurius is a GraphQL adapter for Fastify. It exposes a GraphQL endpoint that handles queries, mutations, and subscriptions over HTTP and WebSocket.

GRAPHQL

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Mercurius Domain Security

TLSv1.3

SECURITY

Resources

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

RateLimits

RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

Company 2

The organization behind the API

Website

Website

LinkedIn

Other 1

Properties that don't map to a standard resource type

Licensing

Licensing

Source (apis.yml)

aid: mercurius
name: Mercurius
description: High-performance GraphQL server for Fastify with Just-In-Time compilation via graphql-jit, automatic query caching,
  N+1 prevention via dataloader integration, federation support, subscription via WebSocket, batched query support, and GraphQL
  Playground integration.
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/mercurius.png
url: https://mercurius.dev/
baseURL: https://mercurius.dev/
created: 2026-06-14
modified: 2026-06-14
specificationVersion: '0.23'
tags:
- GraphQL
- Fastify
- Node.js
- Federation
- WebSocket
- Open-Source
tags_raw:
- GraphQL
- Fastify
- Node.js
- Federation
- WebSocket
- Open Source
apis:
- aid: mercurius:api
  name: Mercurius API
  description: GraphQL adapter for Fastify enabling high-performance GraphQL servers and gateways with JIT compilation, query
    caching, subscriptions, and federation.
  tags:
  - GraphQL
  - Fastify
  - Federation
  - Subscription
  tags_raw:
  - GraphQL
  - Fastify
  - Federation
  - Subscriptions
  humanURL: https://mercurius.dev/
  baseURL: https://mercurius.dev/
  properties:
  - url: https://mercurius.dev/
    type: Documentation
  - url: graphql/mercurius-graphql.md
    type: GraphQL
common:
- type: DomainSecurity
  url: security/mercurius-domain-security.yml
- url: https://mercurius.dev/
  type: Website
- url: https://mercurius.dev/
  type: Documentation
- url: https://www.linkedin.com/company/mercuriusinc
  type: LinkedIn
- url: https://github.com/mercurius-js
  type: GitHubOrganization
- url: https://github.com/mercurius-js/mercurius/blob/master/LICENSE
  type: Licensing
- url: plans/mercurius-plans.md
  type: Plans
- url: rate-limits/mercurius-rate-limits.md
  type: RateLimits
- url: finops/mercurius-finops.md
  type: FinOps
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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