Cap'n Proto C++ Reference Implementation

The C++ reference implementation is the canonical runtime for Cap'n Proto, providing the capnp compiler, serialization library, and KJ/RPC runtime. Other language implementations are maintained by their respective authors and track the C++ reference.

Work with this as data

Every API here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for apis

7 MCP tools reach this
  • find_apisBrowse and filter every API in the catalog.
  • get_api_artifactsOne API's artifacts, grouped by type.
  • get_openapiThe primary OpenAPI for this API.
  • find_similar_apisAPIs that look like this one.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
This API
curl "https://apis.io/api/v1/apis/capn-proto-cpp-runtime"
All apis
curl "https://apis.io/api/v1/apis?limit=25"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

A second provider on the same verified email joins the account you already have.

API entry from apis.yml

apis.yml Raw ↑
aid: capn-proto:capn-proto-cpp-runtime
name: Cap'n Proto C++ Reference Implementation
description: The C++ reference implementation is the canonical runtime for Cap'n Proto, providing the
  capnp compiler, serialization library, and KJ/RPC runtime. Other language implementations are maintained
  by their respective authors and track the C++ reference.
humanURL: https://github.com/capnproto/capnproto
tags:
- IPC
- SDK
- Serialization
tags_raw:
- IPC
- SDKs
- Serialization
properties:
- type: GitHubRepository
  url: https://github.com/capnproto/capnproto
- type: GettingStarted
  url: https://capnproto.org/install.html
- type: Documentation
  url: https://capnproto.org/cxx.html
x-features:
- capnp schema compiler
- KJ async and concurrency library
- RPC runtime over TCP and in-process transports
- Arena allocator for fast message construction
- Packed and canonical encoding support