S2 Dev

S2 ("Stream Store") is the API for unlimited, durable, real-time streams. Where object storage deals with blobs, S2 provides append-able, ordered record streams that can be tailed in real time and replayed from any retained point. Core data-plane operations are append, read, and check-tail; the control plane manages accounts, basins (stream namespaces), streams, scoped access tokens, locations, and metrics. It targets agent session logs, live views and build logs, event sourcing and sync, data feeds, resumable LLM token streaming, and observability. Access is over a REST/JSON + Protobuf HTTP API, an S2S binary protocol over HTTP/2, SSE tailing, first-party TypeScript, Python, Go, and Rust SDKs, a CLI, and a Terraform provider. S2 is a Y Combinator-backed company.

S2 Dev publishes 6 API contracts indexed on the APIs.io network, including Access Tokens API, Basins API, Locations API, and 3 more. Tagged areas include Company, Streaming, Real-Time, Event Streaming, and Durable Storage.

The S2 Dev catalog on APIs.io includes 1 Spectral governance ruleset.

S2 Dev’s developer surface includes authentication, documentation, API reference, getting-started guide, support, engineering blog, pricing, and 36 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

71.9/100 exemplar ▬ flat Agent 33/100 agent ready Front door AI 4/6 moderate Heartbeat 84/100 alive saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessPaid

1 published contract 3 Agent Skills

Company Streaming Real-Time Event StreamingDurable StorageMessage StreamingData Feed Observability Developer Tools Infrastructure

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Developer Platform & API Ecosystem Management

BC-4270

Access Tokens

POST /access-tokens DELETE /access-tokens/{id}

Kin Score

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

Composite quality — 71.9/100 · exemplar

Contract Quality 10.4 / 19

Developer Ergonomics 12.2 / 15

Access Clarity 15.0 / 15

Operational Transparency 7.4 / 10

Contract Governance 1.6 / 9

Discoverability 5.5 / 8

Regulatory Posture 5.3 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 33/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 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 4 / 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 0 / 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
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)
Typed Event Surface +6 pts — AsyncAPI document, OR webhooks/callbacks objects in the as-published OpenAPI, OR common[].type includes Webhooks

6 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 55.4 — up to +11.2 composite points
Contract Governance scores 18.2 — up to +9.8 composite points
Developer Ergonomics scores 81.5 — up to +3.7 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/s2-dev/apis.yml: open an issue on github.com/api-evangelist/s2-dev 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 →

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
Agent Skills (SKILL.md packages)	standard	37.1	-	2
Accelerator Portfolios (Y Combinator, 500 Global, Antler participation)	standard	37.1	-	2

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 1

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.

OpenAPI

measured — observed by APIs.io (published)

APIs 6

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

S2 Dev Access Tokens API

Manage access tokens

S2 Dev Basins API

Manage basins

S2 Dev Locations API

Manage locations

S2 Dev Metrics API

Usage metrics and data.

S2 Dev Records API

Manage records

S2 Dev Streams API

Manage streams

Open Collections 6

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

S2, the durable streams access-tokens API

OPEN COLLECTION

S2, the durable streams access-tokens basins API

OPEN COLLECTION

S2, the durable streams access-tokens locations API

OPEN COLLECTION

S2, the durable streams access-tokens metrics API

OPEN COLLECTION

S2, the durable streams access-tokens records API

OPEN COLLECTION

S2, the durable access-tokens streams API

OPEN COLLECTION

Agent Skills 3

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

Append records and tail a stream on S2

AGENT SKILL

Create a basin and stream on S2

AGENT SKILL

Issue a scoped S2 access token

AGENT SKILL

S2 Dev API pricing

Prices published by S2 Dev, read 2026-10-28 from s2.dev/pricing.

Plan	Price
Storage retained	$0.05
Basin	$0.01
Streams	$0.01
Access tokens	$0.01
Writes Standard	$0.050
Writes Express	$0.075
Reads Private	$0.050
Reads Internet	$0.100

All 11 plans, limits and sources →

Billed by: gib · FinOps profile →

Pricing Plans 2

Published pricing tiers and plan structures.

S2 Dev Plans Pricing

11 plans

PLANS

S2 Dev Price Estimates

0 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

S2 Dev Rate Limits

5 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

S2 Dev

SLA

FinOps 1

Cost, billing, and metering signals for API financial operations.

S2 Dev Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

S2 Dev API Rules

63 rules · 55 errors 6 warnings 2 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.

S2 Dev Openapi Overlay

2 actions · update · s2-dev-openapi-original.json

DERIVED

Security Posture 4

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

S2 Dev Authentication

http · 1 scheme

SECURITY

S2 Dev Domain Security

TLSv1.3 · DMARC

SECURITY

S2 Dev Vulnerability Disclosure

security.txt · contact published

SECURITY

S2 Dev Trust Center

SOC 2, HIPAA, GDPR

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

S2 Dev Agentic Access

24 operations · 12 acting · 1 human-in-the-loop

24 operations · 12 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal

GettingStarted

SignUp

Sandbox

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 5

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

WellKnown

WellKnown

LLMsTxt

LLMsTxt

X-MCPServerCandidate

X-MCPServerCandidate

AgentSkill

AgentSkill

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Lifecycle

Conventions

Idempotency

ErrorCatalog

DataModel

Conformance

Build 5

SDKs, sample code, and the tooling you integrate with

PostmanWorkspace

PostmanWorkspace

GitHubOrganization

Packages

SDKs

CLI

Access & Security 7

Authentication, authorization, and security posture

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

Authentication

Security

TrustCenter

Compliance

SecurityTxt

Scroll for all 7

Operate 4

Status, limits, changes, and where to get help

Support

StatusPage

ChangeLog

RateLimits

Commercial 4

Pricing, plans, and the legal terms of use

Plans

Pricing

TermsOfService

PrivacyPolicy

Company 3

The organization behind the API

BlogRSS

BlogRSS

Website

Website

Blog

Blog

Other 3

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

APICatalog

APICatalog

Overlay

Overlay

Source (apis.yml)

aid: s2-dev
name: S2 Dev
description: S2 ("Stream Store") is the API for unlimited, durable, real-time streams. Where object storage deals with blobs,
  S2 provides append-able, ordered record streams that can be tailed in real time and replayed from any retained point. Core
  data-plane operations are append, read, and check-tail; the control plane manages accounts, basins (stream namespaces),
  streams, scoped access tokens, locations, and metrics. It targets agent session logs, live views and build logs, event sourcing
  and sync, data feeds, resumable LLM token streaming, and observability. Access is over a REST/JSON + Protobuf HTTP API,
  an S2S binary protocol over HTTP/2, SSE tailing, first-party TypeScript, Python, Go, and Rust SDKs, a CLI, and a Terraform
  provider. S2 is a Y Combinator-backed company.
url: https://raw.githubusercontent.com/api-evangelist/s2-dev/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
x-tier: stub
x-tier-reason: portfolio-lead
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: paid
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: high
  source:
  - plans
  - authentication
  - rate-limits
  - security
  - sandbox
  generated: '2026-11-06'
  method: derived
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-10-06'
image: https://avatars.githubusercontent.com/u/136030139?v=4
tags:
- Company
- Streaming
- Real-Time
- Event Streaming
- Durable Storage
- Message Streaming
- Data Feed
- Observability
- Developer Tools
- Infrastructure
tags_raw:
- Company
- Streaming
- Real-Time
- Event Streaming
- Durable Storage
- Message Streaming
- Data Feeds
- Observability
- Developer Tools
- Infrastructure
apis:
- aid: s2-dev:s2-dev-access-tokens-api
  name: S2 Dev Access Tokens API
  description: Manage access tokens
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Access Tokens
  tags_raw:
  - access-tokens
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-access-tokens-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
- aid: s2-dev:s2-dev-basins-api
  name: S2 Dev Basins API
  description: Manage basins
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Basins
  tags_raw:
  - basins
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-basins-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
- aid: s2-dev:s2-dev-locations-api
  name: S2 Dev Locations API
  description: Manage locations
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Location
  tags_raw:
  - locations
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-locations-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
- aid: s2-dev:s2-dev-metrics-api
  name: S2 Dev Metrics API
  description: Usage metrics and data.
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Metrics
  tags_raw:
  - metrics
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-metrics-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
- aid: s2-dev:s2-dev-records-api
  name: S2 Dev Records API
  description: Manage records
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Records
  tags_raw:
  - records
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-records-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
- aid: s2-dev:s2-dev-streams-api
  name: S2 Dev Streams API
  description: Manage streams
  humanURL: https://s2.dev/docs/api
  baseURL: https://a.s2.dev/v1
  tags:
  - Streams
  tags_raw:
  - streams
  properties:
  - type: OpenAPI
    url: openapi/s2-dev-streams-api-openapi.yml
  - type: Protobuf
    url: grpc/s2-dev-s2.proto
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
x-enrichment:
  date: '2026-07-21'
  status: enriched
  artifacts_added: 26
  pass: local-v1
common:
- type: CapabilityMap
  url: capabilities/s2-dev-capability-edges.yml
  name: S2 Dev Business Capability Map
- type: Plans
  url: plans/s2-dev-plans-pricing.yml
- type: PostmanWorkspace
  url: https://www.postman.com/kinlaneapi/s2-dev/overview
- url: https://s2.dev/blog/feed.xml
  type: BlogRSS
- type: Website
  url: https://www.s2.dev/
- type: VulnerabilityDisclosure
  url: security/s2-dev-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/s2-dev-domain-security.yml
- type: AgenticAccess
  url: agentic-access/s2-dev-agentic-access.yml
- type: Authentication
  url: authentication/s2-dev-authentication.yml
- type: Security
  url: https://s2.dev/docs/platform/security
- type: TrustCenter
  url: security/s2-dev-trust-center.yml
- type: Compliance
  url: https://s2.dev/docs/platform/security
- type: DeveloperPortal
  url: https://s2.dev/docs
- type: Documentation
  url: https://s2.dev/docs
- type: APIReference
  url: https://s2.dev/docs/api
- type: GettingStarted
  url: https://s2.dev/docs/quickstart
- type: Support
  url: mailto:hi@s2.dev
- type: Blog
  url: https://s2.dev/blog
- type: GitHubOrganization
  url: https://github.com/s2-streamstore
- type: Pricing
  url: https://s2.dev/pricing
- type: SignUp
  url: https://s2.dev/dashboard
- type: TermsOfService
  url: https://s2.dev/terms
- type: PrivacyPolicy
  url: https://s2.dev/privacy
- type: StatusPage
  url: https://status.s2.dev
- type: Packages
  url: packages/s2-dev-packages.yml
- type: SDKs
  url: packages/s2-dev-packages.yml
- type: CLI
  url: cli/s2-dev-cli.yml
- type: Sandbox
  url: sandbox/s2-dev-sandbox.yml
- type: ChangeLog
  url: changelog/s2-dev-changelog.yml
- type: Lifecycle
  url: lifecycle/s2-dev-lifecycle.yml
- type: RateLimits
  url: rate-limits/s2-dev-rate-limits.yml
- type: Conventions
  url: conventions/s2-dev-conventions.yml
- type: Idempotency
  url: conventions/s2-dev-conventions.yml
- type: ErrorCatalog
  url: errors/s2-dev-problem-types.yml
- type: DataModel
  url: data-model/s2-dev-data-model.yml
- type: Conformance
  url: conformance/s2-dev-conformance.yml
- type: WellKnown
  url: well-known/s2-dev-well-known.yml
- type: SecurityTxt
  url: well-known/s2-dev-security.txt
- type: APICatalog
  url: well-known/s2-dev-api-catalog.json
- type: LLMsTxt
  url: llms/s2-dev-llms.txt
- type: Overlay
  url: overlays/s2-dev-openapi-overlay.yaml
- type: X-MCPServerCandidate
  url: mcp/s2-dev-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/_index.yml

S2 Dev API — frequently asked questions

Does S2 Dev have an API?

Yes. APIs.io lists 6 APIs from S2 Dev, including S2 Dev Access Tokens API, S2 Dev Basins API and S2 Dev Locations API, and 3 more.

Is there an OpenAPI specification for the S2 Dev API?

Yes. APIs.io indexes 6 OpenAPI specifications for S2 Dev, each linked for download from this page.

How do I authenticate with the S2 Dev API?

S2 Dev uses bearer-token authentication (http · 1 scheme). The details are profiled on APIs.io as S2 Dev Authentication.

How much does the S2 Dev API cost?

S2 Dev publishes its prices; its Storage retained plan is $0.05 as of 2026-10-28. APIs.io lists 11 pricing plans for S2 Dev, with each plan's price, limits and inclusions under Pricing on this page.

Is the S2 Dev API ready for AI agents?

S2 Dev has a Kin Score of 71.9 out of 100 (exemplar) and an Agent Readiness score of 32.8 (agent-ready), scored by API Evangelist on 2026-11-06.

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