Ressl website screenshot

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 16 more developer resources.

🌐 Visit website 📡 Source on GitHub
26.4/100 thin ▬ flat Agent 30/100 agent ready Front door AI 4/6 moderate saas Full breakdown ↓
scored 2026-09-25 · rubric v0.23.0
1 APIs
Mock APIsAPI TestingAI AgentsAgent EvaluationSandboxDeveloper ToolsSynthetic DataSoftware-as-a-Service

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-09-25 · rubric v0.23.0
Composite quality — 26.4/100 · thin
Contract Quality 2.8 / 19
Developer Ergonomics 9.3 / 15
Access Clarity 2.0 / 15
Operational Transparency 0.3 / 10
Contract Governance 0.4 / 9
Discoverability 5.5 / 8
Regulatory Posture 2.5 / 15
Create-or-Update Ergonomics 0.0 / 10
Agent readiness — 30/100 · 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
Delegated User Identity 0 / 6
Protected Resource Metadata 0 / 5
Registration Without a Human 0 / 6
Agentic Commerce Well-Known Document 0 / 5
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 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.
The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.
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/ressl-ai: 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.

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

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
 X-MCPServerCandidate
X-MCPServerCandidate
 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 2

The organization behind the API

Website
Website
 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
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - authentication
  - security
  generated: '2026-09-03'
  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: Website
  url: https://www.ressl.ai/
- 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: X-MCPServerCandidate
  url: mcp/ressl-ai-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- 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/

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