feat: Add Python implementation of Dexscreener plugin (#219)

* feat: Add Python implementation of Dexscreener plugin

- Implements all three tools from TypeScript version:
  - search_pairs
  - get_pairs_by_chain_and_pair
  - get_token_pairs_by_token_address
- Follows same structure as Coingecko plugin
- Includes proper error handling and rate limiting
- Adds comprehensive documentation

Testing:
- All tools tested successfully
- Verified functionality matches TypeScript implementation
- Confirmed working with Langchain example (not included in commit)

Co-Authored-By: Agus Armellini Fischer <[email protected]>

* Update README.md

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Agus Armellini Fischer <[email protected]>

python/src/plugins/dexscreener/README.md

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+# GOAT SDK Dexscreener Plugin
+
+This plugin provides tools for interacting with the Dexscreener API, allowing you to:
+- Fetch pairs by chainId and pairId
+- Search for DEX pairs matching a query string
+- Get all DEX pairs for given token addresses
+
+## Installation
+
+```bash
+pip install goat-sdk-plugin-dexscreener
+```
+
+## Usage
+
+```python
+from goat_plugins.dexscreener import dexscreener, DexscreenerPluginOptions
+
+# Initialize the plugin
+plugin = dexscreener(DexscreenerPluginOptions())
+```

python/src/plugins/dexscreener/goat_plugins/dexscreener/__init__.py

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+from dataclasses import dataclass
+from goat.classes.plugin_base import PluginBase
+from .service import DexscreenerService
+
+
+@dataclass
+class DexscreenerPluginOptions:
+    # Dexscreener currently doesn't require any auth keys
+    pass
+
+
+class DexscreenerPlugin(PluginBase):
+    def __init__(self, options: DexscreenerPluginOptions):
+        super().__init__("dexscreener", [DexscreenerService()])
+
+    def supports_chain(self, chain) -> bool:
+        # Dexscreener is a data provider for multiple chains
+        return True
+
+
+def dexscreener(options: DexscreenerPluginOptions) -> DexscreenerPlugin:
+    return DexscreenerPlugin(options)

python/src/plugins/dexscreener/goat_plugins/dexscreener/parameters.py

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+from pydantic import BaseModel, Field
+from typing import List
+
+
+class GetPairsByChainAndPairParameters(BaseModel):
+    chainId: str = Field(
+        ...,
+        description="The chain ID of the pair"
+    )
+    pairId: str = Field(
+        ...,
+        description="The pair ID to fetch"
+    )
+
+
+class SearchPairsParameters(BaseModel):
+    query: str = Field(
+        ...,
+        description="The search query string"
+    )
+
+
+class GetTokenPairsParameters(BaseModel):
+    tokenAddresses: List[str] = Field(
+        ...,
+        max_items=30,
+        description="A list of up to 30 token addresses"
+    )

python/src/plugins/dexscreener/goat_plugins/dexscreener/service.py

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+import aiohttp
+from goat.decorators.tool import Tool
+from .parameters import (
+    GetPairsByChainAndPairParameters,
+    SearchPairsParameters,
+    GetTokenPairsParameters,
+)
+
+
+class DexscreenerService:
+    def __init__(self):
+        self.base_url = "https://api.dexscreener.com/latest/dex"
+
+    async def _fetch(self, url: str, action: str):
+        try:
+            async with aiohttp.ClientSession() as session:
+                async with session.get(url) as response:
+                    if not response.ok:
+                        raise Exception(f"HTTP error! status: {response.status} {await response.text()}")
+                    return await response.json()
+        except Exception as e:
+            raise Exception(f"Failed to {action}: {e}")
+
+    @Tool({
+        "description": "Fetch pairs by chainId and pairId from Dexscreener",
+        "parameters_schema": GetPairsByChainAndPairParameters
+    })
+    async def get_pairs_by_chain_and_pair(self, parameters: dict):
+        url = f"{self.base_url}/pairs/{parameters['chainId']}/{parameters['pairId']}"
+        return await self._fetch(url, "fetch pairs")
+
+    @Tool({
+        "description": "Search for DEX pairs matching a query string on Dexscreener",
+        "parameters_schema": SearchPairsParameters
+    })
+    async def search_pairs(self, parameters: dict):
+        query = parameters["query"]
+        url = f"{self.base_url}/search?q={query}"
+        return await self._fetch(url, "search pairs")
+
+    @Tool({
+        "description": "Get all DEX pairs for given token addresses (up to 30) from Dexscreener",
+        "parameters_schema": GetTokenPairsParameters
+    })
+    async def get_token_pairs_by_token_address(self, parameters: dict):
+        addresses = ",".join(parameters["tokenAddresses"])
+        url = f"{self.base_url}/tokens/{addresses}"
+        return await self._fetch(url, "get token pairs")

python/src/plugins/dexscreener/pyproject.toml

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+[tool.poetry]
+name = "goat-sdk-plugin-dexscreener"
+version = "0.1.1"
+description = "Goat plugin for Dexscreener"
+authors = ["Andrea Villa <[email protected]>"]
+readme = "README.md"
+keywords = ["goat", "sdk", "web3", "agents", "ai"]
+homepage = "https://ohmygoat.dev/"
+repository = "https://github.com/goat-sdk/goat"
+packages = [
+    { include = "goat_plugins/dexscreener" },
+]
+
+[tool.poetry.dependencies]
+python = "^3.10"
+aiohttp = "^3.8.6"
+goat-sdk = "^0.1.1"
+
+[tool.poetry.group.test.dependencies]
+pytest = "^8.3.4"
+pytest-asyncio = "^0.25.0"
+
+[tool.poetry.urls]
+"Bug Tracker" = "https://github.com/goat-sdk/goat/issues"
+
+[tool.pytest.ini_options]
+addopts = [
+    "--import-mode=importlib",
+]
+pythonpath = "src"
+asyncio_default_fixture_loop_scope = "function"
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"
+
+[tool.poetry.group.dev.dependencies]
+ruff = "^0.8.6"
+goat-sdk = { path = "../../goat-sdk", develop = true }
+
+[tool.ruff]
+line-length = 120
+target-version = "py312"