`registerTool`

Problem

When building a tool-using agent, you need a central place to register tools so the agent can find them by name at runtime. Without a registry, you pass tool arrays around everywhere — and one mismatch means the agent silently skips tool calls.

Solution

registerTool adds your tool to a global in-memory registry. Once registered, the agent can look up and execute that tool by name. Registration is validated — duplicate names throw immediately so you catch mistakes at startup, not during a live agent run.

Feature & Use-Case

Use registerTool when:

You want to define tools once at app startup and reference them throughout your agent
You are building a LangChain Node.js app where multiple agents share common tools (e.g. a search tool, a database query tool)
You want name-collision protection — registering the same name twice throws a clear error

Import


import { registerTool } from "llm-layer-engine";

Function Signature


function registerTool(tool: Tool): void

`Tool` Type


type Tool = {
  name: string;
  execute: (input: Record<string, unknown>) => Promise<Record<string, unknown> | string | number | boolean>;
};

Parameters

Parameter	Type	Required	Description
`tool.name`	`string`	✅	Unique name the agent uses to call this tool
`tool.execute`	`Function`	✅	Async function that receives the tool’s input and returns a result

Example — Register Tools at App Startup


import { registerTool } from "llm-layer-engine";
 
// Register a weather tool
registerTool({
  name: "get_weather",
  execute: async (input) => {
    const city = input.city as string;
    // Call your weather API here
    return { city, temperature: "28°C", condition: "Sunny" };
  },
});
 
// Register a search tool
registerTool({
  name: "web_search",
  execute: async (input) => {
    const query = input.query as string;
    // Call your search API here
    return { results: [`Result for: ${query}`] };
  },
});
 
console.log("Tools registered ✓");

Error: Duplicate Tool Name


registerTool({ name: "get_weather", execute: async () => ({}) });
registerTool({ name: "get_weather", execute: async () => ({}) });
// ❌ Throws: "Tool with name get_weather already registered"

Registering Tools for a Specific Agent Run

You can also pass tools directly into reActLoop without using the global registry:


import { reActLoop } from "llm-layer-engine";
 
const loop = reActLoop({
  config,
  provider,
  messages,
  tools: [
    {
      name: "get_weather",
      execute: async (input) => ({ city: input.city, temp: "30°C" }),
    },
  ],
});

Both approaches work. Use the registry for shared tools, pass directly for agent-specific tools.

Conclusion

registerTool is how you wire tools into the global registry. Call it once per tool at app startup. Keep tool names lowercase and snake_case — they must match exactly what your LLM returns in its tool-call responses.

registerTool