Agent Reach Channel Contract: Required Interface for Platform Implementations

Every platform implementation in Agent Reach must inherit from the abstract Channel class defined in agent_reach/channels/base.py and implement four required class attributes, the abstract can_handle() method, and a check() method that initializes the active_backend attribute.

The Panniantong/Agent-Reach repository treats each supported Internet platform—such as YouTube, Twitter, and Reddit—as a channel. To ensure consistent behavior across diverse platforms, the codebase enforces a strict channel contract through an abstract base class and automated validation via tests/test_channel_contracts.py.

Core Requirements of the Channel Contract

All concrete channel implementations must satisfy three categories of requirements: mandatory class attributes, abstract methods, and runtime state management.

Mandatory Class Attributes

Every channel must define four class-level attributes in agent_reach/channels/base.py:

• name: str – A short identifier string (e.g., "youtube" or "twitter") used for registry lookups.
• description: str – A human-readable description of the platform.
• backends: List[str] – An ordered list of possible back-end implementations (e.g., ["yt-dlp"] for YouTube).
• tier: int – An integer defining setup complexity: 0 for zero-config, 1 for requiring a free API key, and 2 for full manual setup.

The active_backend Attribute

Channels must initialize an instance attribute active_backend to None. The check() method is responsible for setting this to a string value from the backends list after probing the environment, indicating which back-end is actually serving the channel.

Abstract Methods

The Channel base class defines two critical methods that subclasses must implement:

can_handle(url: str) -> bool
This method determines whether the channel can process a given URL. It must return a boolean value and is used by the router to delegate URLs to the appropriate platform handler.

check(config=None) -> Tuple[str, str]
This method probes the runtime environment, validates back-end availability, sets active_backend, and returns a tuple containing:

• A status string: "ok", "warn", "off", or "error"
• A human-readable message describing the state

Optional Capabilities

Beyond the core contract, channels may implement additional methods to expose platform-specific features:

read(url: str) -> str
Returns the full content of a URL, typically formatted as Markdown. This is only required for channels that expose raw page data, such as the generic Web channel in agent_reach/channels/web.py.

search(query: str, limit: int = 10) -> list
Performs a platform-wide search and returns a list of result dictionaries. Searchable channels like V2EX and Xueqiu implement this method in their respective files (e.g., agent_reach/channels/v2ex.py).

Base Class Utilities

The base class provides ordered_backends(config=None) -> List[str], which returns a permutation of the backends attribute. If the configuration contains a <channel>_backend override, that back-end is moved to the front of the returned list, allowing user preferences to take precedence without modifying the channel code.

Contract Enforcement via Automated Testing

The tests/test_channel_contracts.py suite validates that every channel adheres to the contract:

• Verifies that name and description are unique, non-empty strings.
• Confirms that backends is a list and tier is an integer in {0, 1, 2}.
• Checks that active_backend exists, starts as None, and after check() is either None or a valid string from backends.
• Asserts that ordered_backends() returns a permutation of backends and respects configuration overrides.
• Validates that can_handle() returns a boolean for representative URLs.

Practical Implementation Examples

Minimal Channel Implementation

The following example demonstrates a minimal valid channel for a fictional Foo platform:

# agent_reach/channels/foo.py

from .base import Channel

class FooChannel(Channel):
    name = "foo"
    description = "Foo platform – example channel"
    backends = ["foo-cli"]
    tier = 1                     # needs a free API key

    def can_handle(self, url: str) -> bool:
        return "foo.com" in url.lower()

    def check(self, config=None):
        # Simple probe – pretend the CLI is always present

        self.active_backend = self.backends[0]
        return "ok", "foo-cli is ready"

This class fulfills the contract by inheriting from Channel, supplying all required attributes, implementing can_handle(), and providing a check() method that sets active_backend.

Consuming Channels via the Public API

All channels expose a uniform interface that calling code can rely on regardless of the underlying platform:

from agent_reach.channels import get_all_channels

# Find the YouTube channel and ask it to handle a URL

yt = next(ch for ch in get_all_channels() if ch.name == "youtube")
assert yt.can_handle("https://youtu.be/dQw4w9WgXcQ")

status, message = yt.check()
print(f"status={status}, message={message}, backend={yt.active_backend}")

Implementing Search Functionality

For platforms that support search, implement the optional method as shown in channels like V2EX:

# In a searchable channel (e.g., V2EX) you would add:

def search(self, query: str, limit: int = 10) -> list:
    # Perform HTTP request to the platform's search endpoint

    # Return a list of dicts with title, url, etc.

    ...

Summary

• The Agent Reach channel contract is defined by the abstract Channel class in agent_reach/channels/base.py.
• All implementations must provide name, description, backends, and tier class attributes.
• The can_handle() method is abstract and must return a boolean to indicate URL support.
• The check() method must probe the environment, set active_backend, and return a status tuple.
• read() and search() are optional methods for content retrieval and platform search.
• The tests/test_channel_contracts.py suite automatically validates compliance for all registered channels.

Frequently Asked Questions

What happens if a channel does not implement can_handle()?

Since can_handle() is declared as an abstract method in the Channel base class, any concrete subclass that fails to implement it will raise a TypeError at instantiation time, preventing incomplete implementations from being registered in the channel registry.

Is the read() method required for all platforms?

No, read() is optional. Only channels that expose raw page content—such as the generic Web channel in agent_reach/channels/web.py—need to implement this method. Platforms like YouTube typically use transcription or API-specific methods instead of raw HTML reading.

How does the test suite validate the tier attribute?

The tests/test_channel_contracts.py file asserts that every channel has a tier attribute with an integer value in the set {0, 1, 2}, ensuring consistent categorization of platforms by their setup complexity (zero-config, free key required, or full setup required).

Can developers override the default backend selection?

Yes, the base class provides ordered_backends() which checks the configuration for a <channel>_backend key. If present, that back-end is moved to the front of the returned list, allowing users to override defaults without modifying the channel implementation.

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  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}