Using Tool Variables

You can use tool variables to specify environment variables available to your custom tools. For example, if you set a tool variable PASSWORD to banana, then write a custom function that prints os.getenv('PASSWORD') in the tool, the function will print banana.

Assigning tool variables in the ADE

To assign tool variables in the Agent Development Environment (ADE), click on Env Vars to open the Environment Variables viewer:

Once in the Environment Variables viewer, click + to add a new tool variable if one does not exist.

Assigning tool variables in the API / SDK

You can also assign tool variables on agent creation in the API with the tool_exec_environment_variables parameter:

{7-9}

curl

curl -X POST https://api.letta.com/v1/agents \
     -H "Authorization: Bearer $LETTA_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
  "memory_blocks": [],
  "llm":"openai/gpt-4o-mini",
  "tool_exec_environment_variables": {
      "API_KEY": "your-api-key-here"
  }
}'

{5-7}

python

agent_state = client.agents.create(
    memory_blocks=[],
    model="openai/gpt-4o-mini",
    tool_exec_environment_variables={
        "API_KEY": "your-api-key-here"
    }
)

TypeScript {5-7}

const agentState = await client.agents.create({
  memoryBlocks: [],
  model: "openai/gpt-4o-mini",
  toolExecEnvironmentVariables: {
    API_KEY: "your-api-key-here",
  },
});