A TypeScript function

What is supported

Any TypeScript or JavaScript on Node.js 22 or 20. A function is the documented path for TypeScript agents, and the way to deploy any library Onecortex does not recognise.

A complete agent

agent.yml

apiVersion: v1
runtime: node22
entrypoint: agent.ts#agent
dependencies: package.json

package.json

{
  "type": "module",
  "dependencies": {}
}

agent.ts

export async function agent(prompt: string): Promise<string> {
  return `You said: ${prompt}`
}

Call any model you like from inside the function, with its key added as a secret on the agent’s Config tab. See Configuration and secrets.

A complete A TypeScript function example

order-status: A plain function with a lookup tool of its own, reported as real tool events.

The prompt and the reply

The function receives the prompt, and a context as its second argument: { sessionId, request }, where request holds prompt, params, surface and messages. What it may return:

Shape	Reply
A string, or a promise of one	The string, once
An async generator yielding strings	Each string as it is yielded
An object with `invoke(prompt)`	What `invoke` returns

Events it reports

Events	From
`text`	Each string you return or yield
Any event	Yield an object with a `type`, and it is sent as that event, checked first
`done` or `error`	The end of the run: always exactly one

See Streaming and events.

The caller’s fields

In context.request.params:

export async function agent(prompt: string, context: { request: { params: Record<string, unknown> } }) {
  const model = String(context.request.params['model'] ?? 'gpt-5')
  return callMyModel(model, prompt)
}

Report tool calls

Yield event objects alongside your text:

export async function* agent(prompt: string) {
  yield { type: 'tool_call_start', id: 'call_1', name: 'lookup_order' }
  yield { type: 'tool_call_args', id: 'call_1', delta: JSON.stringify({ orderId: '1042' }) }
  yield { type: 'tool_call_end', id: 'call_1' }
  yield { type: 'tool_result', id: 'call_1', output: '{"status":"shipped"}' }
  yield 'Order 1042 has shipped.'
}

Each object needs the fields of its event type. v is filled in for you, and Onecortex adds the closing done.

Known limits

An object with a type key is always read as an event. Yield a string to send data that has one.

Troubleshooting

You see	Do this
`Your agent yielded an event Onecortex cannot read: <problem>.`	Fix the field it names.
A file read fails with `ENOENT`	Paths are relative to the agent folder, which is the working directory. Read the file from there.

Get started

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Resources

A TypeScript function

What is supported

A complete agent

A complete A TypeScript function example

The prompt and the reply

Events it reports

The caller’s fields

Report tool calls

Known limits

Troubleshooting

​What is supported

​A complete agent

A complete A TypeScript function example

​The prompt and the reply

​Events it reports

​The caller’s fields

​Report tool calls

​Known limits

​Troubleshooting

What is supported

A complete agent

The prompt and the reply

Events it reports

The caller’s fields

Report tool calls

Known limits

Troubleshooting