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/apis/tools/tools.py

@@ -0,0 +1,141 @@
+# 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 Annotated, Any, Dict, List, Literal, Optional, Union
+
+from llama_models.llama3.api.datatypes import ToolPromptFormat
+from llama_models.schema_utils import json_schema_type, register_schema, webmethod
+from pydantic import BaseModel, Field
+from typing_extensions import Protocol, runtime_checkable
+
+from llama_stack.apis.common.content_types import InterleavedContent, URL
+from llama_stack.apis.resource import Resource, ResourceType
+from llama_stack.providers.utils.telemetry.trace_protocol import trace_protocol
+
+
+@json_schema_type
+class ToolParameter(BaseModel):
+    name: str
+    parameter_type: str
+    description: str
+
+
+@json_schema_type
+class Tool(Resource):
+    type: Literal[ResourceType.tool.value] = ResourceType.tool.value
+    tool_group: str
+    description: str
+    parameters: List[ToolParameter]
+    provider_id: Optional[str] = None
+    metadata: Optional[Dict[str, Any]] = None
+    tool_prompt_format: Optional[ToolPromptFormat] = Field(
+        default=ToolPromptFormat.json
+    )
+
+
+@json_schema_type
+class ToolDef(BaseModel):
+    name: str
+    description: str
+    parameters: List[ToolParameter]
+    metadata: Dict[str, Any]
+    tool_prompt_format: Optional[ToolPromptFormat] = Field(
+        default=ToolPromptFormat.json
+    )
+
+
+@json_schema_type
+class MCPToolGroupDef(BaseModel):
+    """
+    A tool group that is defined by in a model context protocol server.
+    Refer to https://modelcontextprotocol.io/docs/concepts/tools for more information.
+    """
+
+    type: Literal["model_context_protocol"] = "model_context_protocol"
+    endpoint: URL
+
+
+@json_schema_type
+class UserDefinedToolGroupDef(BaseModel):
+    type: Literal["user_defined"] = "user_defined"
+    tools: List[ToolDef]
+
+
+ToolGroupDef = register_schema(
+    Annotated[
+        Union[MCPToolGroupDef, UserDefinedToolGroupDef], Field(discriminator="type")
+    ],
+    name="ToolGroup",
+)
+
+
+class ToolGroup(Resource):
+    type: Literal[ResourceType.tool_group.value] = ResourceType.tool_group.value
+
+
+@json_schema_type
+class ToolInvocationResult(BaseModel):
+    content: InterleavedContent
+    error_message: Optional[str] = None
+    error_code: Optional[int] = None
+
+
+class ToolStore(Protocol):
+    def get_tool(self, tool_name: str) -> Tool: ...
+
+
+@runtime_checkable
+@trace_protocol
+class ToolGroups(Protocol):
+    @webmethod(route="/toolgroups/register", method="POST")
+    async def register_tool_group(
+        self,
+        tool_group_id: str,
+        tool_group: ToolGroupDef,
+        provider_id: Optional[str] = None,
+    ) -> None:
+        """Register a tool group"""
+        ...
+
+    @webmethod(route="/toolgroups/get", method="GET")
+    async def get_tool_group(
+        self,
+        tool_group_id: str,
+    ) -> ToolGroup: ...
+
+    @webmethod(route="/toolgroups/list", method="GET")
+    async def list_tool_groups(self) -> List[ToolGroup]:
+        """List tool groups with optional provider"""
+        ...
+
+    @webmethod(route="/tools/list", method="GET")
+    async def list_tools(self, tool_group_id: Optional[str] = None) -> List[Tool]:
+        """List tools with optional tool group"""
+        ...
+
+    @webmethod(route="/tools/get", method="GET")
+    async def get_tool(self, tool_name: str) -> Tool: ...
+
+    @webmethod(route="/toolgroups/unregister", method="POST")
+    async def unregister_tool_group(self, tool_group_id: str) -> None:
+        """Unregister a tool group"""
+        ...
+
+
+@runtime_checkable
+@trace_protocol
+class ToolRuntime(Protocol):
+    tool_store: ToolStore
+
+    @webmethod(route="/tool-runtime/discover", method="POST")
+    async def discover_tools(self, tool_group: ToolGroupDef) -> List[ToolDef]: ...
+
+    @webmethod(route="/tool-runtime/invoke", method="POST")
+    async def invoke_tool(
+        self, tool_name: str, args: Dict[str, Any]
+    ) -> ToolInvocationResult:
+        """Run a tool with the given arguments"""
+        ...