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 is listed with 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 📡 Profile data on GitHub

16.1/100 emerging ▬ flat Agent 16/100 agent aware saas Full breakdown ↓
scored 2026-10-23 · rubric v0.25.0 · Show this score on your site →

1 API

GraphQLFastifyNode.js Federation WebSocket Open Source

Kin Score

Kin Score How this is scored →
scored 2026-10-23 · rubric v0.25.0

Composite quality — 16.1/100 · emerging

Contract Quality 7.2 / 21

Developer Ergonomics 1.6 / 17

Access Clarity 0.0 / 17

Operational Transparency 0.6 / 11

Contract Governance 0.0 / 10

Discoverability 5.5 / 9

Regulatory Posture 0.9 / 15

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

Pagination 5 / 5

Distinct Operations 3 / 3

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

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.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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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 →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
GraphQL Ecosystem (Foundation, graphql.org listings, public GraphQL APIs)	undeclared	-	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Standards implemented 2

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

GraphQL

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

WebSockets

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

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'
x-docs-platform: docsify
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-10-04
tags:
- GraphQL
- Fastify
- Node.js
- Federation
- WebSocket
- Open Source
tags_raw:
- GraphQL
- Fastify
- Node.js
- Federation
- WebSocket
- Open Source
- 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/
  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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