River Markets

River Markets is a unified prime brokerage for prediction markets, consolidating multiple exchanges — Kalshi, Polymarket, and Polymarket US (with Novig and Rothera planned) — behind a single account, order-management system, and REST + WebSocket API. Every contract across all venues is assigned a unified River ID, so professional and institutional traders can search markets, place and route orders (including icebergs, pegs, stop-losses, and take-profits with smart order routing), track positions and P&L across isolated subaccounts, and stream live fills, orderbooks, orders, and trade prints from one integration. Requests are Ed25519-signed so the private key never leaves the client process. Founded by ex-BlackRock and high-frequency trading quants and backed by Y Combinator (Spring 2026).

River Markets publishes 13 APIs on the APIs.io network, including balance API, complex-orders API, fair-values API, and 10 more. Tagged areas include Company, Prediction Markets, Trading, Prime Brokerage, and Financial Services.

The River Markets catalog on APIs.io includes 1 event-driven AsyncAPI specification.

River Markets’ developer surface includes documentation, API reference, getting-started guide, signup flow, authentication, and 17 more developer resources.

🌐 Visit website 📡 Source on GitHub
43.2/100 thin ▬ flat Agent 71/100 agent native Full breakdown ↓
scored 2026-07-27 · rubric v0.5
AccessSelf serve
13 APIs 1 MCP Servers
CompanyPrediction MarketsTradingPrime BrokerageFinancial ServicesOrder ManagementMarket DataWebSocketFintech

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 43.2/100 · thin
Contract Quality 17.5 / 25
Developer Ergonomics 13.5 / 20
Commercial Clarity 2.6 / 20
Operational Transparency 0.7 / 13
Governance 0.0 / 12
Discoverability 10.0 / 10
Agent readiness — 71/100 · agent native
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 12 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 8 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 6 / 6
Agent Skills 5 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
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/river-markets: 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 13

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

River Markets balance API

The balance API from River Markets — 1 operation(s) for balance.

River Markets complex-orders API

Manage complex orders: conditional orders (take-profit and stop-loss), TWAP, and other advanced order types.

River Markets fair-values API

The fair-values API from River Markets — 2 operation(s) for fair-values.

River Markets fills API

Retrieve trade execution history and fill details.

River Markets generic-assets API

The generic-assets API from River Markets — 3 operation(s) for generic-assets.

River Markets markets API

Search and discover prediction markets across Kalshi and Polymarket.

River Markets orderbooks API

The orderbooks API from River Markets — 2 operation(s) for orderbooks.

River Markets orders API

Place and manage orders on prediction market exchanges.

River Markets positions API

View current portfolio positions across all connected exchanges.

River Markets prices API

Get historical price data and candlesticks from exchanges.

River Markets subaccounts API

Manage trading subaccounts. Each subaccount can have its own exchange credentials and positions.

River Markets tradeprints API

Recent trades for a market. Pairs with the /v1/ws/tradeprints WebSocket for live updates.

River Markets watchlists API

The watchlists API from River Markets — 4 operation(s) for watchlists.

Scroll for all 13

MCP Servers 1

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

river-markets-mcp.yml

MCP SERVER

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

River Markets Streaming API

Real-time WebSocket streams over wss://api.rivermarkets.com. Client frames are JSON text; server frames are orjson-serialized UTF-8 bytes. Handshake auth uses the Ed25519 signed...

ASYNCAPI

Security Posture 2

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

River Markets Authentication

apiKey/http · 4 schemes

SECURITY

River Markets Domain Security

TLSv1.3 · DMARC

SECURITY

Agentic Access 1

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

River Markets Agentic Access

48 operations · 24 acting

48 operations · 24 acting

AGENTIC

Resources

Get Started 3

Portal, sign-up, and the first successful call

DeveloperPortal
DeveloperPortal
 GettingStarted
GettingStarted
 SignUp
SignUp

Documentation 4

Reference material describing how the API behaves

Documentation
Documentation
 APIReference
APIReference
 OpenAPI
OpenAPI
 AsyncAPI
AsyncAPI

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt
LLMsTxt
 MCPServer
MCPServer
 AgenticAccess
AgenticAccess
 AgentSkill
AgentSkill

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Conventions
Conventions
 ErrorCatalog
ErrorCatalog
 Lifecycle
Lifecycle
 Conformance
Conformance
 DataModel
DataModel

Build 3

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization
 Packages
Packages
 SDKs
SDKs

Access & Security 2

Authentication, authorization, and security posture

Authentication
Authentication
 DomainSecurity
DomainSecurity

Other 1

Properties that don't map to a standard resource type

Overlay
Overlay

Source (apis.yml)

apis.yml Raw ↑ 
aid: river-markets
name: River Markets
description: River Markets is a unified prime brokerage for prediction markets, consolidating multiple exchanges — Kalshi,
  Polymarket, and Polymarket US (with Novig and Rothera planned) — behind a single account, order-management system, and REST
  + WebSocket API. Every contract across all venues is assigned a unified River ID, so professional and institutional traders
  can search markets, place and route orders (including icebergs, pegs, stop-losses, and take-profits with smart order routing),
  track positions and P&L across isolated subaccounts, and stream live fills, orderbooks, orders, and trade prints from one
  integration. Requests are Ed25519-signed so the private key never leaves the client process. Founded by ex-BlackRock and
  high-frequency trading quants and backed by Y Combinator (Spring 2026).
url: https://raw.githubusercontent.com/api-evangelist/river-markets/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
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
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-21'
x-enrichment:
  date: '2026-07-21'
  status: enriched
  artifacts_added: 17
  pass: local-v1
image: https://rivermarkets.com/favicon.ico
tags:
- Company
- Prediction Markets
- Trading
- Prime Brokerage
- Financial Services
- Order Management
- Market Data
- WebSocket
- Fintech
apis:
- aid: river-markets:river-markets-balance-api
  name: River Markets balance API
  description: The balance API from River Markets — 1 operation(s) for balance.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - balance
  properties:
  - type: OpenAPI
    url: openapi/river-markets-balance-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-complex-orders-api
  name: River Markets complex-orders API
  description: 'Manage complex orders: conditional orders (take-profit and stop-loss), TWAP, and other advanced order types.'
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - complex-orders
  properties:
  - type: OpenAPI
    url: openapi/river-markets-complex-orders-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-fair-values-api
  name: River Markets fair-values API
  description: The fair-values API from River Markets — 2 operation(s) for fair-values.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - fair-values
  properties:
  - type: OpenAPI
    url: openapi/river-markets-fair-values-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-fills-api
  name: River Markets fills API
  description: Retrieve trade execution history and fill details.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - fills
  properties:
  - type: OpenAPI
    url: openapi/river-markets-fills-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-generic-assets-api
  name: River Markets generic-assets API
  description: The generic-assets API from River Markets — 3 operation(s) for generic-assets.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - generic-assets
  properties:
  - type: OpenAPI
    url: openapi/river-markets-generic-assets-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-markets-api
  name: River Markets markets API
  description: Search and discover prediction markets across Kalshi and Polymarket.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - markets
  properties:
  - type: OpenAPI
    url: openapi/river-markets-markets-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-orderbooks-api
  name: River Markets orderbooks API
  description: The orderbooks API from River Markets — 2 operation(s) for orderbooks.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - orderbooks
  properties:
  - type: OpenAPI
    url: openapi/river-markets-orderbooks-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-orders-api
  name: River Markets orders API
  description: Place and manage orders on prediction market exchanges.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - orders
  properties:
  - type: OpenAPI
    url: openapi/river-markets-orders-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-positions-api
  name: River Markets positions API
  description: View current portfolio positions across all connected exchanges.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - positions
  properties:
  - type: OpenAPI
    url: openapi/river-markets-positions-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-prices-api
  name: River Markets prices API
  description: Get historical price data and candlesticks from exchanges.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - prices
  properties:
  - type: OpenAPI
    url: openapi/river-markets-prices-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-subaccounts-api
  name: River Markets subaccounts API
  description: Manage trading subaccounts. Each subaccount can have its own exchange credentials and positions.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - subaccounts
  properties:
  - type: OpenAPI
    url: openapi/river-markets-subaccounts-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-tradeprints-api
  name: River Markets tradeprints API
  description: Recent trades for a market. Pairs with the /v1/ws/tradeprints WebSocket for live updates.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - tradeprints
  properties:
  - type: OpenAPI
    url: openapi/river-markets-tradeprints-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
- aid: river-markets:river-markets-watchlists-api
  name: River Markets watchlists API
  description: The watchlists API from River Markets — 4 operation(s) for watchlists.
  humanURL: https://docs.rivermarkets.com
  baseURL: https://api.rivermarkets.com
  tags:
  - watchlists
  properties:
  - type: OpenAPI
    url: openapi/river-markets-watchlists-api-openapi.yml
  - type: Documentation
    url: https://docs.rivermarkets.com
  - type: APIReference
    url: https://docs.rivermarkets.com/api-reference/overview
  - type: GettingStarted
    url: https://docs.rivermarkets.com/quickstart
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: DeveloperPortal
  url: https://docs.rivermarkets.com
- type: Documentation
  url: https://docs.rivermarkets.com
- type: APIReference
  url: https://docs.rivermarkets.com/api-reference/overview
- type: GettingStarted
  url: https://docs.rivermarkets.com/quickstart
- type: SignUp
  url: https://app.rivermarkets.com
- type: GitHubOrganization
  url: https://github.com/rivermarkets
- type: OpenAPI
  url: openapi/river-markets-openapi-original.json
- type: Authentication
  url: authentication/river-markets-authentication.yml
- type: DomainSecurity
  url: security/river-markets-domain-security.yml
- type: LLMsTxt
  url: llms/river-markets-llms.txt
- type: Packages
  url: packages/river-markets-packages.yml
- type: SDKs
  url: packages/river-markets-packages.yml
- type: Conventions
  url: conventions/river-markets-conventions.yml
- type: ErrorCatalog
  url: errors/river-markets-problem-types.yml
- type: Lifecycle
  url: lifecycle/river-markets-lifecycle.yml
- type: Conformance
  url: conformance/river-markets-conformance.yml
- type: DataModel
  url: data-model/river-markets-data-model.yml
- type: MCPServer
  url: mcp/river-markets-mcp.yml
- type: Overlay
  url: overlays/river-markets-openapi-overlay.yaml
- type: AgenticAccess
  url: agentic-access/river-markets-agentic-access.yml
- type: AsyncAPI
  url: asyncapi/river-markets-streaming-asyncapi.yml
- type: AgentSkill
  url: skills/_index.yml