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

The Ressl catalog on APIs.io includes 1 Spectral governance ruleset.

Ressl’s developer surface includes authentication, documentation, API reference, getting-started guide, signup flow, support, and 16 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

28.1/100 thin ▬ flat Agent 30/100 agent ready Front door AI 4/6 moderate saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

1 published contract 1 Agent Skills

Mock APIsAPI Testing AI Agents Agent Evaluation Sandbox Developer Tools Synthetic Data Software-as-a-Service

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 28.1/100 · thin

Contract Quality 2.8 / 19

Developer Ergonomics 9.3 / 15

Access Clarity 2.0 / 15

Operational Transparency 0.3 / 10

Contract Governance 1.6 / 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

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

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/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document

8 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 15.0 — up to +21.3 composite points
Access Clarity scores 13.2 — up to +17.4 composite points
Operational Transparency scores 2.6 — up to +12.7 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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 the provider profile at artifacts.apis.io/ressl-ai/apis.yml: open an issue on github.com/api-evangelist/ressl-ai to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

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.

Agent Skills

measured — observed by APIs.io (published)

OpenAPI

measured — observed by APIs.io (published)

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 2

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

Ressl Platform Providers API

OPEN COLLECTION

Ressl Platform Providers Snapshots API

OPEN COLLECTION

Agent Skills 1

Packaged agent skills for driving this provider's APIs from an AI assistant.

ressl

AGENT SKILL

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Ressl API Rules

60 rules · 58 errors 1 warnings 1 info

SPECTRAL

OpenAPI Overlays 1

Overlays applied on top of this provider's contracts. Each card says who wrote it: a document the provider publishes, or one API Evangelist derived or generated.

Ressl Ai Platform Overlay

2 actions · update · ressl-ai-platform-openapi.yml

DERIVED

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

Conventions

Lifecycle

Conformance

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

Other 1

Properties that don't map to a standard resource type

Overlay

Overlay

Source (apis.yml)

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: '2026-11-06'
  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-docs-platform: mintlify
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-10-04
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/

Ressl API — frequently asked questions

Does Ressl have an API?

Yes. APIs.io lists 2 APIs from Ressl, including Ressl Providers API and Ressl Snapshots API.

Is there an OpenAPI specification for the Ressl API?

Yes. APIs.io indexes 2 OpenAPI specifications for Ressl, each linked for download from this page.

How do I authenticate with the Ressl API?

Ressl uses bearer-token authentication (apiKey/http · 2 schemes). The details are profiled on APIs.io as Ressl Ai Authentication.

Is the Ressl API ready for AI agents?

Ressl has a Kin Score of 28.1 out of 100 (thin) and an Agent Readiness score of 29.9 (agent-ready), scored by API Evangelist on 2026-11-06.

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