Resources Server

The Resources server is the “world” the agent interacts with. It defines the task, the tools and actions available to the agent, and the verification logic that evaluates performance and returns reward signals for training.

1
# Resources Server - pseudocode
2
class MyResourceServer(SimpleResourcesServer):
3
    
4
    # Initialize the "sandbox" for this specific rollout
5
    async def seed_session(self, session_id, task_data):
6
        self.state[session_id] = initialize_environment(task_data)
7
8
    # Define tool implementations
9
    async def my_tool(self, session_id, tool_args):
10
        result = execute_action(self.state[session_id], tool_args)
11
        return result
12
13
    # Define verification logic
14
    async def verify(self, session_id, response, ground_truth):
15
        # 1. Extract what the agent actually did
16
        actual_outcome = self.state[session_id].get_final_state()
17
        
18
        # 2. Reward if the actual outcome matches expected outcome
19
        if actual_outcome == ground_truth:
20
            return reward(1.0)
21
        return reward(0.0)

Session Management

NeMo Gym uses a session_id to maintain isolated state for every parallel rollout. This ensures that concurrent rollouts never interfere with each other, and for multi-step environments, preserves state across steps within a single rollout.

Tool Implementations

Tools are exposed as HTTP endpoints that the Agent server calls during a rollout. Each tool receives the session_id to access the correct rollout state, executes an action, and returns the result as an observation back to the model. Tools may also mutate the session state (e.g., updating a database), which the verifier can later inspect to evaluate performance.

Verification Logic

Every Resources server implements a verify() function that evaluates the result of a rollout and returns a reward signal for training.

For semantic or rubric-based scoring, verify() can call a second language model (LLM-as-Judge). For configuration, deployment, and implementation patterns, refer to LLM-as-Judge.

Examples

See Example Resources Servers for concrete Resources Servers and the task, action, and verification patterns they demonstrate.

Server Configuration