Connect-RPC

Connect is a slim framework for building browser-friendly and gRPC-compatible HTTP APIs from Protocol Buffer schemas. Servers built with Connect speak the Connect protocol, gRPC, and gRPC-Web simultaneously, while clients can switch between protocols without changing code. Connect provides type-safe SDKs for Go, TypeScript/JavaScript, Swift, Kotlin, and Python, plus the Buf-generated `protoc-gen-connect-*` code generators. The project is open source under the Apache 2.0 license and is maintained by Buf.

Connect-RPC is listed with 5 APIs on the APIs.io network. Tagged areas include Apache 2.0, Buf, Code Generation, Connect Protocol, and gRPC.

Connect-RPC’s developer surface includes documentation, engineering blog, and 11 more developer resources.

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13.5/100 emerging ▬ flat Agent 1/100 human only Front door AI 1/6 silent Heartbeat 100/100 alive Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreemium

5 APIs

Apache 2.0BufCode GenerationConnect ProtocolgRPCgRPC-WebHTTP Open Source Protocol Buffers RPC SDK

Kin Score

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

Composite quality — 13.5/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 4.9 / 17

Access Clarity 1.3 / 17

Operational Transparency 1.2 / 11

Contract Governance 0.0 / 10

Discoverability 5.3 / 9

Regulatory Posture 0.9 / 15

Agent readiness — 1/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 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 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
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
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)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes

12 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 0.0 — up to +25.0 composite points
Access Clarity scores 7.9 — up to +18.4 composite points
Developer Ergonomics scores 28.6 — up to +14.3 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/connect-rpc/apis.yml: open an issue on github.com/api-evangelist/connect-rpc 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
Buf Schema Registry (public Protocol Buffers modules, gRPC / ConnectRPC schema publishers)	standard	34.5 (thin)	-	-

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 4

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.

gRPC

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

HTTP

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

Protocol Buffers

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

RPC

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

APIs 5

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

connect-go

The Go implementation of Connect. Provides server handlers and clients that speak the Connect, gRPC, and gRPC-Web protocols simultaneously. Generated from .proto files via the p...

connect-es (Connect for ECMAScript)

Connect for ECMAScript provides type-safe browser and Node.js clients and Node.js servers from Protobuf schemas. Targets the Connect protocol and gRPC-Web with idiomatic TypeScr...

connect-swift

Connect for Swift provides type-safe Connect, gRPC, and gRPC-Web clients for iOS, macOS, watchOS, and tvOS apps, generated from Protobuf schemas via protoc-gen-connect-swift.

connect-kotlin

Connect for Kotlin provides type-safe clients for Android and JVM applications. Speaks the Connect protocol, gRPC, and gRPC-Web from a single SDK generated by protoc-gen-connect...

connect-python

Connect for Python (beta) provides Connect protocol and gRPC clients generated from Protobuf schemas. Targets ASGI servers and async Python with type-safe stubs.

Connect-RPC API pricing

Not yet checked against Connect-RPC's own pricing page. Compiled by API Evangelist on 2026-05-04; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free freemium	Free
Professional paid	Free
Enterprise enterprise	—

Plan details, limits and sources →

Rate limits

Free Tier Default: 10 requests per minute
Free Tier Monthly Quota: 1000 requests per month
Professional Tier Default: 100 requests per minute

Compiled by API Evangelist, not yet checked against Connect-RPC's documentation. All 5 limits →

Pricing Plans 1

Published pricing tiers and plan structures.

Connect Rpc Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Connect Rpc Rate Limits

5 limits

RATE LIMITS

FinOps 1

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

Connect Rpc Finops

FINOPS

Security Posture 1

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

Connect Rpc Domain Security

TLSv1.3 · HSTS

SECURITY

Resources

Get Started 1

Portal, sign-up, and the first successful call

Demo

Demo

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 2

Status, limits, changes, and where to get help

RateLimits

RateLimits

Slack

Slack

Commercial 3

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

License

License

Company 3

The organization behind the API

Website

Website

Blog

Blog

BlogRSS

BlogRSS

Other 1

Properties that don't map to a standard resource type

Maintainer

Maintainer

Source (apis.yml)

aid: connect-rpc
name: Connect-RPC
description: Connect is a slim framework for building browser-friendly and gRPC-compatible HTTP APIs from Protocol Buffer
  schemas. Servers built with Connect speak the Connect protocol, gRPC, and gRPC-Web simultaneously, while clients can switch
  between protocols without changing code. Connect provides type-safe SDKs for Go, TypeScript/JavaScript, Swift, Kotlin, and
  Python, plus the Buf-generated `protoc-gen-connect-*` code generators. The project is open source under the Apache 2.0 license
  and is maintained by Buf.
type: Index
deliveryModel:
  model: unknown
  license_evidence:
    not_product:
    - connectrpc/connect-es
    - connectrpc/connect-go
    - connectrpc/connect-kotlin
    - connectrpc/connect-python
    - connectrpc/connect-swift
  open_source: unknown
  commercial: false
  callable_host: false
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - repository-not-product
  generated: '2026-09-25'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: low
  source:
  - plans
  - security
  generated: '2026-11-06'
  method: derived
position: Producing
access: Open Source
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/connect-rpc.png
url: https://raw.githubusercontent.com/api-evangelist/connect-rpc/refs/heads/main/apis.yml
created: '2026-03-25'
modified: '2026-04-28'
specificationVersion: '0.23'
kind: opensource
tags:
- Apache 2.0
- Buf
- Code Generation
- Connect Protocol
- gRPC
- gRPC-Web
- HTTP
- Open Source
- Protocol Buffers
- RPC
- SDK
tags_raw:
- Apache 2.0
- Buf
- Code Generation
- Connect Protocol
- gRPC
- gRPC-Web
- HTTP
- Open Source
- Protocol Buffers
- RPC
- SDKs
- Open-Source
apis:
- aid: connect-rpc:connect-go
  name: connect-go
  description: The Go implementation of Connect. Provides server handlers and clients that speak the Connect, gRPC, and gRPC-Web
    protocols simultaneously. Generated from .proto files via the protoc-gen-connect-go plugin and designed to slot into idiomatic
    net/http servers.
  humanURL: https://connectrpc.com/docs/go/
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  tags:
  - Go
  - SDK
  properties:
  - type: Documentation
    url: https://connectrpc.com/docs/go/
  - type: GettingStarted
    url: https://connectrpc.com/docs/go/getting-started
  - type: GitHub
    url: https://github.com/connectrpc/connect-go
  - type: Tutorial
    url: https://connectrpc.com/docs/go/tutorial
  x-features:
  - Connect Protocol Server and Client
  - gRPC Compatibility
  - gRPC-Web Compatibility
  - Streaming RPCs
  - Interceptors
  - Idiomatic net/http Integration
  x-use-cases:
  - Build a Go service callable from browsers and gRPC clients
  - Migrate gRPC services to Connect without breaking clients
  - Add HTTP/JSON access to existing Protobuf services
- aid: connect-rpc:connect-es
  name: connect-es (Connect for ECMAScript)
  description: Connect for ECMAScript provides type-safe browser and Node.js clients and Node.js servers from Protobuf schemas.
    Targets the Connect protocol and gRPC-Web with idiomatic TypeScript types and tree-shakable output.
  humanURL: https://connectrpc.com/docs/web/
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  tags:
  - JavaScript
  - SDK
  - TypeScript
  properties:
  - type: Documentation
    url: https://connectrpc.com/docs/web/
  - type: GettingStarted
    url: https://connectrpc.com/docs/web/getting-started
  - type: GitHub
    url: https://github.com/connectrpc/connect-es
  x-features:
  - Browser Clients
  - Node.js Clients
  - Node.js Servers
  - Tree-Shakable Bundles
  - Type-Safe TypeScript
  - gRPC-Web Compatibility
  x-use-cases:
  - Call Protobuf services from React, Vue, or vanilla JS
  - Build Node.js servers without a gRPC dependency
  - Share TypeScript types between client and server
- aid: connect-rpc:connect-swift
  name: connect-swift
  description: Connect for Swift provides type-safe Connect, gRPC, and gRPC-Web clients for iOS, macOS, watchOS, and tvOS
    apps, generated from Protobuf schemas via protoc-gen-connect-swift.
  humanURL: https://connectrpc.com/docs/swift/
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  tags:
  - iOS
  - SDK
  - Swift
  properties:
  - type: Documentation
    url: https://connectrpc.com/docs/swift/
  - type: GettingStarted
    url: https://connectrpc.com/docs/swift/getting-started
  - type: GitHub
    url: https://github.com/connectrpc/connect-swift
  x-features:
  - URLSession Integration
  - Streaming Support
  - gRPC and gRPC-Web Clients
  - Async/Await API
  x-use-cases:
  - Call Protobuf services from iOS apps
  - Add streaming RPC to Apple platform clients
- aid: connect-rpc:connect-kotlin
  name: connect-kotlin
  description: Connect for Kotlin provides type-safe clients for Android and JVM applications. Speaks the Connect protocol,
    gRPC, and gRPC-Web from a single SDK generated by protoc-gen-connect-kotlin.
  humanURL: https://connectrpc.com/docs/kotlin/
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  tags:
  - Android
  - JVM
  - Kotlin
  - SDK
  properties:
  - type: Documentation
    url: https://connectrpc.com/docs/kotlin/
  - type: GettingStarted
    url: https://connectrpc.com/docs/kotlin/getting-started
  - type: GitHub
    url: https://github.com/connectrpc/connect-kotlin
  x-features:
  - Coroutines API
  - OkHttp Transport
  - Streaming Support
  - Multi-Protocol Client
  x-use-cases:
  - Call Protobuf services from Android apps
  - Share Kotlin types across mobile and backend
- aid: connect-rpc:connect-python
  name: connect-python
  description: Connect for Python (beta) provides Connect protocol and gRPC clients generated from Protobuf schemas. Targets
    ASGI servers and async Python with type-safe stubs.
  humanURL: https://connectrpc.com/docs/python/
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  tags:
  - Python
  - SDK
  properties:
  - type: Documentation
    url: https://connectrpc.com/docs/python/
  - type: GitHub
    url: https://github.com/connectrpc/connect-python
  x-features:
  - ASGI Integration
  - Type-Safe Stubs
  - Connect and gRPC Clients
  x-use-cases:
  - Add Protobuf RPC to Python services
  - Call Connect services from data-science notebooks
common:
- type: Plans
  url: plans/connect-rpc-plans-pricing.yml
- type: RateLimits
  url: rate-limits/connect-rpc-rate-limits.yml
- type: FinOps
  url: finops/connect-rpc-finops.yml
- type: DomainSecurity
  url: security/connect-rpc-domain-security.yml
- type: Website
  url: https://connectrpc.com
- type: Documentation
  url: https://connectrpc.com/docs/introduction
- type: GitHubOrganization
  url: https://github.com/connectrpc
- type: Demo
  url: https://connectrpc.com/demo
- type: Blog
  url: https://buf.build/blog
- url: https://buf.build/blog/rss.xml
  type: BlogRSS
  description: Discovered RSS/Atom feed for https://buf.build/blog
- type: Maintainer
  url: https://buf.build
- type: License
  url: https://github.com/connectrpc/connect-go/blob/main/LICENSE
- type: Slack
  url: https://buf.build/links/slack
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

Connect-RPC API — frequently asked questions

Does Connect-RPC have an API?

Yes. APIs.io lists 5 APIs from Connect-RPC, including connect-go, connect-es (Connect for ECMAScript) and connect-swift, and 2 more.

How much does the Connect-RPC API cost?

APIs.io lists 3 pricing plans for Connect-RPC, with each plan's price, limits and inclusions under Pricing on this page.

Is the Connect-RPC API ready for AI agents?

Connect-RPC has a Kin Score of 13.5 out of 100 (emerging) and an Agent Readiness score of 0.6 (human-only), scored by API Evangelist on 2026-11-06.

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