Your first skill

A skill is a folder with a manifest.json, a SKILL.md and one module per tool. This page builds a small one end to end; Skill authoring is the complete reference.

1. Layout

greeter/
  manifest.json
  SKILL.md
  tools/greet.ts
  tests/greet.test.ts

2. Manifest

{
  "specVersion": 1,
  "namespace": "yourname",
  "name": "greeter",
  "version": "0.1.0",
  "description": "Friendly greetings for agents",
  "license": "MIT",
  "runtime": { "type": "node", "minNodeVersion": "22.18.0" },
  "permissions": { "fs": { "read": [], "write": [] }, "network": [], "env": [] },
  "tools": [
    {
      "name": "greet",
      "description": "Greet someone by name",
      "entry": "tools/greet.ts",
      "input": {
        "type": "object",
        "properties": { "name": { "type": "string", "minLength": 1, "maxLength": 100 } },
        "required": ["name"],
        "additionalProperties": false
      },
      "output": {
        "type": "object",
        "properties": { "text": { "type": "string" } },
        "required": ["text"]
      }
    }
  ]
}

The empty permissions mean the tool gets no files, no network, no environment and no host capabilities. The runtime validates input against input before the tool starts, and output against output after it returns.

3. Tool

// tools/greet.ts — default export: (input, context) => JSON-serializable output
export default async function greet(input: { name: string }) {
  return { text: `Hello, ${input.name}!` };
}

TypeScript is stripped at load time; use erasable syntax only (no enum or namespace).

4. Test

// tests/greet.test.ts
import assert from "node:assert/strict";
import { test } from "node:test";
import greet from "../tools/greet.ts";

test("greets", async () => {
  assert.deepEqual(await greet({ name: "Ada" }), { text: "Hello, Ada!" });
});

node --test tests/*.test.ts

5. Validate and publish

splice publish ./greeter --dry-run

The dry run validates the manifest, schemas, file paths and archive exactly like the registry will. Publishing needs a registry token (Publishing); published versions are immutable.

Using data without keys

To read chain data, prices or web results, declare host capabilities instead of network access — the host runs them with its own provider keys (Host capabilities):

"permissions": { "network": [], "env": [], "capabilities": ["market.price"] }

export default async function price(input: { token: string }, ctx) {
  return ctx.capability("market.price", { token: input.token });
}