cxp 3.0.0

Capability Exchange Protocol

CXP: Capability Exchange Protocol

CXP is a semantic interoperability protocol for software components. It allows libraries, runtimes, and services to publish their capabilities and telemetry through a small shared contract.

Why CXP?

Modern components are often black boxes. CXP gives them two explicit surfaces:

• Capabilities: So an orchestrator can understand what a component can do.
• Telemetry: So an orchestrator can observe what is happening at runtime.

CXP acts as a semantic bridge, allowing tools like AI agents, test runners, or orchestrators to operate against a shared contract instead of provider-specific assumptions.

Design Goals

• Small Core: Keep the protocol surface narrow and stable.
• High Fidelity: Support expressive catalogs with metadata schemas, shared DTOs, and structured telemetry vocabularies.
• Data-Oriented: Exchange typed data using msgspec for high performance.
• Omnichannel: From cloud runtimes (ASGI/SQL) to industrial hardware (Zebra/Konica).

Installation

pip install cxp

Catalog Layers

CXP includes a growing suite of first-party catalogs organized in six logical layers:

Each layer exposes a family catalog (the abstract contract) plus one or more concrete catalogs that satisfy it.

1. Computing: execution/plan-run, runtime/environment (secrets/resources), and the application/http family with concrete application/asgi, application/wsgi, and application/http-framework catalogs.
2. Persistence: database/sql, database/mongodb (both satisfying database/common), storage/blob, cache/key-value.
3. Communications: transport/http (with the transport/http-family umbrella and transport/websocket sibling), messaging/event-bus (concrete: messaging/nats), and notification/common (concrete: notification/web-push, notification/mobile-push).
4. Queueing: queue/task-engine for background processing.
5. Experience & Media: browser/automation (concrete: browser/playwright), media/video-streaming (HLS/DASH).
6. Industrial: printing/manager (concrete: printing/label for Zebra/ZPL, printing/production for Konica Minolta).

For the full list of registered interfaces and operations, see docs/catalogs/index.md.

Quick Start

from cxp import (
    Capability,
    CapabilityMatrix,
    ComponentIdentity,
    HandshakeRequest,
    get_catalog,
    negotiate_with_provider_catalog,
)

# Resolve the standard catalog for the interface
catalog = get_catalog("database/sql")
assert catalog is not None

# Build the orchestrator request
request = HandshakeRequest(
    client_identity=ComponentIdentity(
        interface="database/sql",
        provider="my-orchestrator",
        version="1.0.0",
    ),
    required_capabilities=("transactions",),
)

# Negotiate with a provider
# response = negotiate_with_provider_catalog(request, my_sql_provider, catalog)

Key Features

1. Structured Error Reporting (CxpError)

Shared machine-readable error envelopes for catalogs that opt into the semantic layer.

if response.error and response.error.retryable:
    # Orchestrator can decide to retry automatically
    await retry_operation()

2. High-Fidelity Results

Many first-party operations return structured data defined in results.py (for example HttpResponse, DbCursor, AsyncWorkReport).

3. Bidirectional Validation

Catalogs can define input_schema and result_schema for operations when the domain benefits from explicit request/response contracts.

Documentation

See docs/index.md for the full documentation set:

• Protocol Overview
• Structured Errors
• Interface Catalogs

License

MIT