Ressl

Ressl (ressl.ai) is a Y Combinator-backed platform that provisions hosted mock SaaS APIs for AI agents and evaluations. Its control-plane API lets you list the mock providers your organization is granted (for example jira, salesforce, slack, plus UI clones of Gmail Business and LinkedIn) and create a short-lived snapshot of one provider that returns a public HTTPS base URL your agent can call - no real customer tenant required. Snapshots carry deterministic or seeded synthetic data and expire on a TTL (default one hour, up to seven days). Control traffic runs on simulation.ressl.ai; provisioned mock traffic is served from *.mock.ressl.cc. Ressl helps teams train, benchmark, and deploy autonomous agents by giving them realistic SaaS surfaces to act against safely.

Ressl publishes 2 APIs on the APIs.io network: Providers API and Snapshots API. Tagged areas include Mock APIs, API Testing, AI Agents, Agent Evaluation, and Sandbox.

Ressl’s developer surface includes authentication, documentation, API reference, getting-started guide, signup flow, support, and 15 more developer resources.

🌐 Visit website 📡 Source on GitHub
40.3/100 developing ▬ flat Agent 41/100 agent ready Full breakdown ↓
scored 2026-08-21 · rubric v0.12.0
AccessSelf serve
2 APIs 1 MCP Servers
Mock APIsAPI TestingAI AgentsAgent EvaluationSandboxDeveloper ToolsSynthetic DataSoftware-as-a-Service

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-21 · rubric v0.12.0
Composite quality — 40.3/100 · developing
Contract Quality 15.4 / 25
Developer Ergonomics 12.4 / 20
Access Clarity 2.6 / 20
Operational Transparency 0.3 / 13
Contract Governance 2.0 / 12
Discoverability 7.6 / 10
Agent readiness — 41/100 · agent ready
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 7 / 7
Rate-Limit Signaling 0 / 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
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/ressl-ai: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 2

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

Ressl Providers API

Discover mock SaaS providers granted to your organization

Ressl Snapshots API

Provision short-lived hosted mock SaaS APIs

Open Collections 3

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

API Collection

OPEN COLLECTION

Ressl Platform Providers API

OPEN COLLECTION

Ressl Platform Providers Snapshots API

OPEN COLLECTION

MCP Servers 1

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

Ressl MCP Server

MCP SERVER

Security Posture 2

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

Ressl Ai Authentication

apiKey/http · 2 schemes

SECURITY

Ressl Ai Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Resources

Get Started 3

Portal, sign-up, and the first successful call

GettingStarted
GettingStarted
 DeveloperPortal
DeveloperPortal
 SignUp
SignUp

Documentation 3

Reference material describing how the API behaves

OpenAPI
OpenAPI
 Documentation
Documentation
 APIReference
APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

WellKnown
WellKnown
 MCPServer
MCPServer
 AgentSkill
AgentSkill
 LLMsTxt
LLMsTxt

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

ErrorCatalog
ErrorCatalog
 Conventions
Conventions
 Lifecycle
Lifecycle
 Conformance
Conformance
 DataModel
DataModel

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity
 Authentication
Authentication

Operate 1

Status, limits, changes, and where to get help

Support
Support

Company 1

The organization behind the API

LinkedIn
LinkedIn

Other 1

Properties that don't map to a standard resource type

Overlay
Overlay

Source (apis.yml)

apis.yml Raw ↑ 
aid: ressl-ai
accessModel:
  pricing: unknown
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: medium
  source:
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/ressl-ai.png
name: Ressl
description: Ressl (ressl.ai) is a Y Combinator-backed platform that provisions hosted mock SaaS APIs for AI agents and evaluations.
  Its control-plane API lets you list the mock providers your organization is granted (for example jira, salesforce, slack,
  plus UI clones of Gmail Business and LinkedIn) and create a short-lived snapshot of one provider that returns a public HTTPS
  base URL your agent can call - no real customer tenant required. Snapshots carry deterministic or seeded synthetic data
  and expire on a TTL (default one hour, up to seven days). Control traffic runs on simulation.ressl.ai; provisioned mock
  traffic is served from *.mock.ressl.cc. Ressl helps teams train, benchmark, and deploy autonomous agents by giving them
  realistic SaaS surfaces to act against safely.
url: https://raw.githubusercontent.com/api-evangelist/ressl-ai/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-20'
x-enrichment:
  date: '2026-07-20'
  status: enriched
  artifacts_added: 13
  pass: local-v1
tags:
- Mock APIs
- API Testing
- AI Agents
- Agent Evaluation
- Sandbox
- Developer Tools
- Synthetic Data
- Software-as-a-Service
tags_raw:
- Mock APIs
- API Testing
- AI Agents
- Agent Evaluation
- Sandbox
- Developer Tools
- Synthetic Data
- SaaS
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
apis:
- aid: ressl-ai:ressl-ai-providers-api
  name: Ressl Providers API
  description: Discover mock SaaS providers granted to your organization
  humanURL: https://docs.ressl.ai
  baseURL: https://simulation.ressl.ai
  tags:
  - Providers
  properties:
  - type: OpenAPI
    url: openapi/ressl-ai-providers-api-openapi.yml
  - type: Documentation
    url: https://docs.ressl.ai
  - type: APIReference
    url: https://docs.ressl.ai/api-reference/authentication
  - type: Quickstart
    url: https://docs.ressl.ai/quickstart
- aid: ressl-ai:ressl-ai-snapshots-api
  name: Ressl Snapshots API
  description: Provision short-lived hosted mock SaaS APIs
  humanURL: https://docs.ressl.ai
  baseURL: https://simulation.ressl.ai
  tags:
  - Snapshots
  properties:
  - type: OpenAPI
    url: openapi/ressl-ai-snapshots-api-openapi.yml
  - type: Documentation
    url: https://docs.ressl.ai
  - type: APIReference
    url: https://docs.ressl.ai/api-reference/authentication
  - type: Quickstart
    url: https://docs.ressl.ai/quickstart
common:
- type: DomainSecurity
  url: security/ressl-ai-domain-security.yml
- type: Authentication
  url: authentication/ressl-ai-authentication.yml
- type: OpenAPI
  url: openapi/_original/ressl-ai-platform-openapi.yml
- type: Overlay
  url: overlays/ressl-ai-platform-overlay.yaml
- type: ErrorCatalog
  url: errors/ressl-ai-problem-types.yml
- type: Conventions
  url: conventions/ressl-ai-conventions.yml
- type: Lifecycle
  url: lifecycle/ressl-ai-lifecycle.yml
- type: Conformance
  url: conformance/ressl-ai-conformance.yml
- type: DataModel
  url: data-model/ressl-ai-data-model.yml
- type: WellKnown
  url: well-known/ressl-ai-well-known.yml
- type: MCPServer
  url: mcp/ressl-ai-mcp.yml
- type: AgentSkill
  url: skills/ressl-ai-skill.md
- type: LLMsTxt
  url: llms/ressl-ai-llms.txt
- type: Documentation
  url: https://docs.ressl.ai
- type: APIReference
  url: https://docs.ressl.ai/api-reference/authentication
- type: GettingStarted
  url: https://docs.ressl.ai/quickstart
- type: DeveloperPortal
  url: https://simulation.ressl.ai
- type: SignUp
  url: https://simulation.ressl.ai
- type: GitHubOrganization
  url: https://github.com/ressl-ai
- type: Support
  url: https://join.slack.com/t/resslaiaiagen-czp2639/shared_invite/zt-2vpd5vabp-D9LpsJZRiweb7_OFnvIvhA
- type: LinkedIn
  url: https://www.linkedin.com/company/ressl-ai/

Work with this as data

Every provider here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for providers

9 MCP tools reach this
  • find_providersBrowse and filter every provider in the catalog.
  • get_provider_artifactsEvery artifact this provider publishes, grouped by type.
  • get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
  • get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
  • get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
  • get_provider_ratingPRO — composite, band, trend and facet scores.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools

Call it yourself

curl for this page
This provider 
curl "https://apis.io/api/v1/providers/ressl-ai"
All providers 
curl "https://apis.io/api/v1/providers?limit=25"
Every operation they expose 
curl "https://apis.io/api/v1/providers/ressl-ai/operations?limit=25"
How their score was established 
curl "https://apis.io/api/v1/providers/ressl-ai/evidence"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no email required.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.