bellwether-markets

Bellwether Markets provides a unified API that aggregates prediction market data from major platforms like Kalshi and Polymarket. By normalizing disparate schemas into a single, developer‑friendly REST and MCP interface, it enables easy access to market listings, detailed market data, and cross‑venue arbitrage opportunities. The service offers free tier access with generous rate limits, supporting both real‑time data retrieval and integration into AI agents for automated trading strategies. Backed by YC and built after Polymarket’s acquisition, Bellwether aims to simplify the fragmented prediction market landscape for developers and traders alike.

bellwether-markets is listed with 1 API on the APIs.io network. Tagged areas include Company, Prediction-Market, API, FinTech, and Data-Aggregation.

The bellwether-markets catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

bellwether-markets’ developer surface includes documentation, API reference, pricing, and 12 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

23.4/100 emerging Agent 14/100 agent aware Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

1 API 1 MCP Servers

CompanyPrediction-MarketAPIFinTechData-Aggregation

Kin Score

Kin Score How this is scored →
scored 2026-10-31 · rubric v0.25.0

Composite quality — 23.4/100 · emerging

Contract Quality 1.4 / 21

Developer Ergonomics 3.9 / 17

Access Clarity 1.8 / 17

Operational Transparency 0.0 / 11

Contract Governance 8.1 / 10

Discoverability 5.2 / 9

Regulatory Posture 1.6 / 15

Agent readiness — 14/100 · agent aware

Machine-Readable Contract 0 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 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

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 could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% 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):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
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)
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link

9 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 6.7 — up to +23.3 composite points
Access Clarity scores 10.5 — up to +17.9 composite points
Developer Ergonomics scores 23.1 — up to +15.4 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/bellwether-markets/apis.yml: open an issue on github.com/api-evangelist/bellwether-markets 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 →

APIs 1

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

Bellwether Markets API

Unified prediction-market data API aggregating Kalshi and Polymarket.

MCP Servers 1

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

bellwether-markets MCP Server

Remote MCP server at mcp.baseframelabs.com.

MCP SERVER

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Bellwether Markets Context

2 classes · 6 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

bellwether-markets API Rules

9 rules · 7 errors 1 warnings 1 info

SPECTRAL

Security Posture 1

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

Bellwether Markets Domain Security

TLSv1.3

SECURITY

Agentic Access 1

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

Bellwether Markets Agentic Access

4 operations

4 operations · 0 acting

AGENTIC

Resources

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 3

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

AgentSkill

AgentSkill

MCPServer

MCPServer

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

ErrorCatalog

Conformance

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Commercial 1

Pricing, plans, and the legal terms of use

Pricing

Pricing

Company 1

The organization behind the API

Website

Website

Other 1

Properties that don't map to a standard resource type

Hosts

Hosts

Source (apis.yml)

aid: bellwether-markets
name: bellwether-markets
description: Bellwether Markets provides a unified API that aggregates prediction market data from major platforms like Kalshi
  and Polymarket. By normalizing disparate schemas into a single, developer‑friendly REST and MCP interface, it enables easy
  access to market listings, detailed market data, and cross‑venue arbitrage opportunities. The service offers free tier access
  with generous rate limits, supporting both real‑time data retrieval and integration into AI agents for automated trading
  strategies. Backed by YC and built after Polymarket’s acquisition, Bellwether aims to simplify the fragmented prediction
  market landscape for developers and traders alike.
url: https://artifacts.apis.io/bellwether-markets/apis.yml
x-type: company
x-source: harvest:mcp-registry
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-30 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-30'
modified: '2026-10-30'
tags:
- Company
- Prediction-Market
- API
- FinTech
- Data-Aggregation
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: AgenticAccess
  url: agentic-access/bellwether-markets-agentic-access.yml
- type: Spectral
  url: rules/bellwether-markets-rules.yml
- type: JSONLD
  url: json-ld/bellwether-markets-context.jsonld
- type: Vocabulary
  url: vocabulary/bellwether-markets-vocabulary.yml
- type: AgentSkill
  url: skills/_index.yml
- type: DataModel
  url: data-model/bellwether-markets-data-model.yml
- type: ErrorCatalog
  url: errors/bellwether-markets-problem-types.yml
- type: Conformance
  url: conformance/bellwether-markets-conformance.yml
- type: MCPServer
  url: mcp/bellwether-markets-mcp.yml
- type: Hosts
  url: hosts/bellwether-markets-hosts.yml
- type: DomainSecurity
  url: security/bellwether-markets-domain-security.yml
- type: Website
  url: https://bellwether.markets/
- type: Documentation
  url: https://bellwether.markets/docs
- type: APIReference
  url: https://api.bellwether.markets/docs
- type: Pricing
  url: https://buy.stripe.com/eVq28s7MKbIg5J64mk3cc01
apis:
- name: Bellwether Markets API
  description: Unified prediction-market data API aggregating Kalshi and Polymarket.
  humanURL: https://bellwether.markets/docs
  baseURL: https://api.bellwether.markets
  aid: bellwether-markets:bellwether-markets-api
x-enrichment:
  date: '2026-10-30'
  status: enriched
  artifacts_added: 16
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

bellwether-markets API — frequently asked questions

Does bellwether-markets have an API?

Yes. APIs.io lists 1 API from bellwether-markets, including Bellwether Markets API.

Does bellwether-markets have an MCP server?

Yes. APIs.io lists 1 MCP server for bellwether-markets: Remote MCP server at mcp.baseframelabs.com.

Is the bellwether-markets API ready for AI agents?

bellwether-markets has a Kin Score of 23.4 out of 100 (emerging) and an Agent Readiness score of 13.5 (agent-aware), scored by API Evangelist on 2026-10-31.

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