Tool Registry

ELI5 - The Vibe Check

A tool registry is the menu an agent reads before deciding what to order. It's a catalog of every tool the agent is allowed to call and exactly what arguments each one expects, so the model can't accidentally invent a function that doesn't exist or guess wrong about how to call the one that does.

Real Talk

A tool registry is the catalog of tool or function definitions, meaning names, descriptions, and JSON schemas for arguments, exposed to an LLM agent at inference time, from which the model selects and invokes tools. MCP servers, function-calling APIs, and agent frameworks all implement some form of tool registry, and it's effectively what determines the full set of actions an agent is even capable of taking.

Show Me The Code

{
  "name": "create_pull_request",
  "description": "Opens a PR from the current branch against main.",
  "parameters": {
    "type": "object",
    "properties": {
      "title": { "type": "string" },
      "body": { "type": "string" }
    },
    "required": ["title"]
  }
}

When You'll Hear This

"The agent only has three tools in its registry, so it can't do anything you didn't explicitly allow." / "We added a new function to the tool registry and the agent started using it immediately."