# AT Protocol

**Canonical:** https://apis.io/providers/at-protocol/  
**Website:** https://atproto.com/  
**APIs profiled:** 12

The AT Protocol (atproto) is an open, federated networking protocol for social applications, originally developed by Bluesky Social PBC and the Bluesky team. It defines a decentralized architecture where user identity and data are portable across providers, anchored in DIDs, signed records, and content-addressed storage. The protocol is composed of independently operable services — Personal Data Servers (PDS), Relays (firehose aggregators), and AppViews (read-side indexers) — that communicate using XRPC and exchange records described by Lexicon schemas. Bluesky (bsky.app) is the reference application built on AT Protocol, but the protocol is designed for any social or social-adjacent application that wants user-owned identity, portable data, and an open federation model. Official and community SDKs exist for TypeScript, Go, Python, Rust, Dart, Swift, C#/.NET, Ruby, PHP, and more, and the full lexicon, network topology, and reference implementations are open source.

## Kin Score — 40.3 / 100 (developing)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 40.3).

| Facet | Score |
|---|---|
| Discoverability | 74.1 |
| Contract Quality | 52.2 |
| Governance | 11.4 |
| Contract Governance | 11.4 |
| Operational Transparency | 50.0 |
| Developer Ergonomics | 31.0 |
| Commercial Clarity | 28.9 |
| Access Clarity | 28.9 |

## Agent readiness — 30.3 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | derived |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | yes |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | no |
| Rate Limit Signal | documented |
| Event Surface Described | derived |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## Access

Free · Self-serve signup — onboarding: self-serve, pricing: free, trial: no (confidence: high).

## APIs (12)

- **AT Protocol XRPC API** — XRPC is the AT Protocol's HTTP-based remote procedure call layer. All protocol interactions — querying records, writing records, subscribing to streams, resolving identity, mode...
- **AT Protocol Lexicon Schemas** — Lexicon is the schema definition language for AT Protocol. Every record type, XRPC method, and event subscription on the network is described by a Lexicon document, which acts a...
- **Personal Data Server (PDS) API** — The PDS hosts a user's repository of signed records and exposes the com.atproto.* XRPC methods for account creation, authentication, record CRUD, blob upload, and repository syn...
- **AT Protocol Relay & Firehose** — The Relay aggregates the com.atproto.sync.subscribeRepos firehose across PDS hosts and re-broadcasts the combined event stream over WebSocket. AppViews and indexers subscribe to...
- **Bluesky AppView API** — The Bluesky AppView indexes the firehose and exposes the app.bsky.* XRPC methods that the Bluesky client (and any compatible client) uses to render timelines, threads, profiles,...
- **AT Protocol Identity (DID & Handles)** — Identity in AT Protocol is anchored in DIDs (did:plc or did:web), with human-readable handles resolved through DNS TXT records or well-known HTTP endpoints. The protocol specifi...
- **AT Protocol Actor API** — Bluesky actor profiles (app.bsky.actor.*)
- **AT Protocol Feed API** — Bluesky feeds, posts, and threads (app.bsky.feed.*)
- **AT Protocol Graph API** — Follow, mute, and block graph (app.bsky.graph.*)
- **AT Protocol Identity API** — DID and handle resolution (com.atproto.identity.*)
- **AT Protocol Repo API** — Repository record CRUD (com.atproto.repo.*)
- **AT Protocol Server API** — Session and account management (com.atproto.server.*)

## Agentic access (1)

- **At Protocol Agentic Access** — 20 operations · 8 acting · 3 human-in-the-loop

## Security (2)

- **At Protocol Authentication** — http · 1 scheme
- **At Protocol Domain Security** — TLSv1.3 · DMARC

## Plans (1)

- **At Protocol Plans Pricing**

## Tags

At-Protocol, atproto, Bluesky, Federation, Decentralized Social, Social Networking, DID, Lexicon, XRPC, PDS, Relay, AppView, Open Protocol

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/at-protocol/). Scores are computed from the provider's own public artifacts under a published rubric.