Tools API with brave and MCP providers (#639)

This PR adds a new Tools api and adds two tool runtime providers: brave
and MCP.

Test plan:
```
curl -X POST 'http://localhost:5000/alpha/toolgroups/register' \
-H 'Content-Type: application/json' \
-d '{ "tool_group_id": "simple_tool",
  "tool_group": {
    "type": "model_context_protocol",
    "endpoint": {"uri": "http://localhost:56000/sse"}
  },
  "provider_id": "model-context-protocol"
}'

 curl -X POST 'http://localhost:5000/alpha/toolgroups/register' \
-H 'Content-Type: application/json' \
-d '{
  "tool_group_id": "search", "provider_id": "brave-search",
  "tool_group": {
    "type": "user_defined",
    "tools": [
      {
        "name": "brave_search",
        "description": "A web search tool",
        "parameters": [
          {
            "name": "query",
            "parameter_type": "string",
            "description": "The query to search"
          }
        ],
        "metadata": {},
        "tool_prompt_format": "json"
      }
    ]
  }
}'

 curl -X GET http://localhost:5000/alpha/tools/list | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   662  100   662    0     0   333k      0 --:--:-- --:--:-- --:--:--  646k
[
  {
    "identifier": "brave_search",
    "provider_resource_id": "brave_search",
    "provider_id": "brave-search",
    "type": "tool",
    "tool_group": "search",
    "description": "A web search tool",
    "parameters": [
      {
        "name": "query",
        "parameter_type": "string",
        "description": "The query to search"
      }
    ],
    "metadata": {},
    "tool_prompt_format": "json"
  },
  {
    "identifier": "fetch",
    "provider_resource_id": "fetch",
    "provider_id": "model-context-protocol",
    "type": "tool",
    "tool_group": "simple_tool",
    "description": "Fetches a website and returns its content",
    "parameters": [
      {
        "name": "url",
        "parameter_type": "string",
        "description": "URL to fetch"
      }
    ],
    "metadata": {
      "endpoint": "http://localhost:56000/sse"
    },
    "tool_prompt_format": "json"
  }
]

curl -X POST 'http://localhost:5000/alpha/tool-runtime/invoke' \
-H 'Content-Type: application/json' \
-d '{
    "tool_name": "fetch",
    "args": {
        "url": "http://google.com/"
    }
}'

 curl -X POST 'http://localhost:5000/alpha/tool-runtime/invoke' \
-H 'Content-Type: application/json' -H 'X-LlamaStack-ProviderData: {"api_key": "<KEY>"}' \
-d '{
    "tool_name": "brave_search",
    "args": {
        "query": "who is meta ceo"
    }
}'
```

llama_stack/providers/remote/tool_runtime/model_context_protocol/__init__.py

@@ -0,0 +1,21 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from pydantic import BaseModel
+
+from .config import ModelContextProtocolConfig
+
+from .model_context_protocol import ModelContextProtocolToolRuntimeImpl
+
+
+class ModelContextProtocolToolProviderDataValidator(BaseModel):
+    api_key: str
+
+
+async def get_adapter_impl(config: ModelContextProtocolConfig, _deps):
+    impl = ModelContextProtocolToolRuntimeImpl(config)
+    await impl.initialize()
+    return impl

llama_stack/providers/remote/tool_runtime/model_context_protocol/config.py

@@ -0,0 +1,11 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from pydantic import BaseModel
+
+
+class ModelContextProtocolConfig(BaseModel):
+    pass

llama_stack/providers/remote/tool_runtime/model_context_protocol/model_context_protocol.py

@@ -0,0 +1,84 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from typing import Any, Dict, List
+from urllib.parse import urlparse
+
+from llama_stack.apis.tools import (
+    MCPToolGroupDef,
+    ToolDef,
+    ToolGroupDef,
+    ToolInvocationResult,
+    ToolParameter,
+    ToolRuntime,
+)
+from llama_stack.providers.datatypes import ToolsProtocolPrivate
+
+from mcp import ClientSession
+from mcp.client.sse import sse_client
+
+from .config import ModelContextProtocolConfig
+
+
+class ModelContextProtocolToolRuntimeImpl(ToolsProtocolPrivate, ToolRuntime):
+    def __init__(self, config: ModelContextProtocolConfig):
+        self.config = config
+
+    async def initialize(self):
+        pass
+
+    async def discover_tools(self, tool_group: ToolGroupDef) -> List[ToolDef]:
+        if not isinstance(tool_group, MCPToolGroupDef):
+            raise ValueError(f"Unsupported tool group type: {type(tool_group)}")
+
+        tools = []
+        async with sse_client(tool_group.endpoint.uri) as streams:
+            async with ClientSession(*streams) as session:
+                await session.initialize()
+                tools_result = await session.list_tools()
+                for tool in tools_result.tools:
+                    parameters = []
+                    for param_name, param_schema in tool.inputSchema.get(
+                        "properties", {}
+                    ).items():
+                        parameters.append(
+                            ToolParameter(
+                                name=param_name,
+                                parameter_type=param_schema.get("type", "string"),
+                                description=param_schema.get("description", ""),
+                            )
+                        )
+                    tools.append(
+                        ToolDef(
+                            name=tool.name,
+                            description=tool.description,
+                            parameters=parameters,
+                            metadata={
+                                "endpoint": tool_group.endpoint.uri,
+                            },
+                        )
+                    )
+        return tools
+
+    async def invoke_tool(
+        self, tool_name: str, args: Dict[str, Any]
+    ) -> ToolInvocationResult:
+        tool = await self.tool_store.get_tool(tool_name)
+        if tool.metadata is None or tool.metadata.get("endpoint") is None:
+            raise ValueError(f"Tool {tool_name} does not have metadata")
+        endpoint = tool.metadata.get("endpoint")
+        if urlparse(endpoint).scheme not in ("http", "https"):
+            raise ValueError(f"Endpoint {endpoint} is not a valid HTTP(S) URL")
+
+        async with sse_client(endpoint) as streams:
+            async with ClientSession(*streams) as session:
+                await session.initialize()
+                result = await session.call_tool(tool.identifier, args)
+
+        return ToolInvocationResult(
+            content="\n".join([result.model_dump_json() for result in result.content]),
+            error_code=1 if result.isError else 0,
+        )