Playground API — Free Stateful Mock REST & GraphQL Service

A free, zero-configuration, stateful mock REST and GraphQL API sandbox by Nilesh Kumar / Niles Labs. Unlike static mock APIs, it provides stateful per-session virtual mutation overlays where POST/PUT/PATCH/DELETE mutations persist across GET queries within a session, while the global baseline dataset remains read-only. Includes chaos/network simulation, dynamic collections, avatar/thumbnail generators, and simulated JWT auth loops. MIT licensed, no auth or signup required.

Playground API — Free Stateful Mock REST & GraphQL Service publishes 1 API on the APIs.io network: Playground REST API. Tagged areas include Developer Tools, Testing, Mock API, api-sandbox, and REST.

Playground API — Free Stateful Mock REST & GraphQL Service’s developer surface includes getting-started guide, sandbox, authentication, and 16 more developer resources.

🌐 Visit website 📡 Source on GitHub
31.5/100 thin Agent 22/100 agent aware Full breakdown ↓
scored 2026-09-14 · rubric v0.22.0
2 APIs 1 MCP Servers
Developer ToolsTestingMock APIapi-sandboxRESTGraphQLE2E Testing

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-09-14 · rubric v0.22.0
Composite quality — 31.5/100 · thin
Contract Quality 9.6 / 23
Developer Ergonomics 8.5 / 18
Access Clarity 3.8 / 18
Operational Transparency 0.6 / 12
Contract Governance 0.5 / 11
Discoverability 6.0 / 9
Create-or-Update Ergonomics 0.0 / 10
Agent readiness — 22/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 0 / 10
Documented Reversibility 0 / 6
MCP Server 0 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 8 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 5 / 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 applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.
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/playground: 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 2

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

Playground REST API

Free stateful mock REST API with session-scoped mutation overlays, dynamic collections, media generators, chaos simulation, and simulated JWT auth. Canonical HTTPS base is playg...

Playground GraphQL API

GraphQL gateway providing stateful mock query and mutation access to the same dataset, with an interactive explorer.

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

Playground API — Free Stateful Mock REST & GraphQL Service MCP Server

MCP SERVER

Pricing Plans 1

Published pricing tiers and plan structures.

Playground Plans Pricing

1 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Playground Rate Limits

0 limits

RATE LIMITS

Security Posture 2

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

Playground Authentication

1 scheme

SECURITY

Playground Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Resources

Get Started 2

Portal, sign-up, and the first successful call

GettingStarted
GettingStarted
 Sandbox
Sandbox

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

AgentSkill
AgentSkill
 MCPServer
MCPServer

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Conformance
Conformance
 DataModel
DataModel
 Lifecycle
Lifecycle
 ErrorCatalog
ErrorCatalog
 Conventions
Conventions

Build 4

SDKs, sample code, and the tooling you integrate with

SourceCode
SourceCode
 GitHubOrganization
GitHubOrganization
 ToolCrosswalk
ToolCrosswalk
 Packages
Packages

Access & Security 2

Authentication, authorization, and security posture

Authentication
Authentication
 DomainSecurity
DomainSecurity

Operate 1

Status, limits, changes, and where to get help

RateLimits
RateLimits

Commercial 1

Pricing, plans, and the legal terms of use

Plans
Plans

Company 1

The organization behind the API

Website
Website

Other 1

Properties that don't map to a standard resource type

Overlay
Overlay

Source (apis.yml)

apis.yml Raw ↑ 
name: Playground API — Free Stateful Mock REST & GraphQL Service
description: A free, zero-configuration, stateful mock REST and GraphQL API sandbox by Nilesh Kumar / Niles Labs. Unlike static
  mock APIs, it provides stateful per-session virtual mutation overlays where POST/PUT/PATCH/DELETE mutations persist across
  GET queries within a session, while the global baseline dataset remains read-only. Includes chaos/network simulation, dynamic
  collections, avatar/thumbnail generators, and simulated JWT auth loops. MIT licensed, no auth or signup required.
url: https://raw.githubusercontent.com/api-evangelist/playground/refs/heads/main/apis.yml
created: '2026-09-14'
modified: '2026-09-14'
specificationVersion: '0.21'
tags:
- Developer Tools
- Testing
- Mock API
- api-sandbox
- REST
- GraphQL
- E2E Testing
tags_raw:
- developer-tools
- testing
- mock-api
- api-sandbox
- rest
- graphql
- e2e-testing
apis:
- name: Playground REST API
  description: Free stateful mock REST API with session-scoped mutation overlays, dynamic collections, media generators, chaos
    simulation, and simulated JWT auth. Canonical HTTPS base is playground.nileslabs.com/api/v1 (OpenAPI/Postman servers value
    declares a raw Vercel origin).
  humanURL: https://playground.nileslabs.com/docs
  baseURL: https://playground.nileslabs.com/api/v1
  tags:
  - Developer Tools
  - Testing
  - Mock API
  - api-sandbox
  - REST
  - GraphQL
  - E2E Testing
  tags_raw:
  - developer-tools
  - testing
  - mock-api
  - api-sandbox
  - rest
  - graphql
  - e2e-testing
  properties:
  - type: OpenAPI
    url: https://playground.nileslabs.com/api/v1/downloads/openapi.json
  - type: PostmanCollection
    url: https://playground.nileslabs.com/api/v1/downloads/postman.json
  - type: Documentation
    url: https://playground.nileslabs.com/docs
  - type: LLMsTxt
    url: https://playground.nileslabs.com/llms.txt
- name: Playground GraphQL API
  description: GraphQL gateway providing stateful mock query and mutation access to the same dataset, with an interactive
    explorer.
  humanURL: https://playground.nileslabs.com/docs/graphql
  baseURL: https://playground.nileslabs.com/api/v1/graphql
  tags:
  - Developer Tools
  - Testing
  - Mock API
  - api-sandbox
  - REST
  - GraphQL
  - E2E Testing
  tags_raw:
  - developer-tools
  - testing
  - mock-api
  - api-sandbox
  - rest
  - graphql
  - e2e-testing
  properties:
  - type: GraphQL
    url: https://playground.nileslabs.com/api/v1/graphql
  - type: Documentation
    url: https://playground.nileslabs.com/docs/graphql
maintainers:
- FN: Nilesh Kumar
  url: https://nileslabs.com
x-generated:
  by: apis.io/add
  model: claude-opus-4-8
  confidence: 97
  at: '2026-09-14T09:54:24.885Z'
common:
- type: Website
  url: https://playground.nileslabs.com
- type: GettingStarted
  url: https://playground.nileslabs.com/docs/quickstart
- type: SourceCode
  url: https://github.com/nileslabs/playground_api
- type: GitHubOrganization
  url: https://github.com/nileslabs
- type: AgentSkill
  url: skills/_index.yml
- type: Overlay
  url: overlays/playground-openapi-overlay.yaml
- type: ToolCrosswalk
  url: mcp/playground-tool-crosswalk.yml
- type: MCPServer
  url: mcp/playground-mcp.yml
- type: Packages
  url: packages/playground-packages.yml
- type: Sandbox
  url: sandbox/playground-sandbox.yml
- type: Conformance
  url: conformance/playground-conformance.yml
- type: Plans
  url: plans/playground-plans-pricing.yml
- type: RateLimits
  url: rate-limits/playground-rate-limits.yml
- type: DataModel
  url: data-model/playground-data-model.yml
- type: Lifecycle
  url: lifecycle/playground-lifecycle.yml
- type: ErrorCatalog
  url: errors/playground-problem-types.yml
- type: Conventions
  url: conventions/playground-conventions.yml
- type: Authentication
  url: authentication/playground-authentication.yml
- type: DomainSecurity
  url: security/playground-domain-security.yml
x-enrichment:
  date: '2026-09-14'
  status: enriched
  artifacts_added: 23
  pass: local-v3

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