---
title: "DF0014: Invalid Agent Field"
description: "RPC function \"{name}\" has an invalid agent field: description must be a non-empty string."
canonical_url: "https://devfra.me/errors/df0014"
---
# DF0014: Invalid Agent Field

> RPC function "\{name}" has an invalid agent field: description must be a non-empty string.

## Message

> RPC function "`{name}`" has an invalid `agent` field: `description` must be a non-empty string.

## Cause

An RPC function opts into agent exposure with an `agent` field, but its required `description` is missing or empty. Agents rely on the description to decide when to invoke a tool.

## Example

```ts
defineRpcFunction({
  name: 'rolldown-get-session-summary',
  type: 'query',
  agent: {
    description: '', // ❌ empty
  },
  // ...
})
```

## Fix

Provide a non-empty `description` (\~1–3 sentences) explaining what the tool does and when agents should invoke it, or remove the `agent` field to keep it RPC-only.

```ts
defineRpcFunction({
  name: 'rolldown-get-session-summary',
  type: 'query',
  agent: {
    description: 'Summarize a Rolldown build session by its id. Safe to call freely.',
  },
  // ...
})
```

## Source

- [`packages/devframe/src/node/host-agent.ts`](https://github.com/devframes/devframe/blob/main/packages/devframe/src/node/host-agent.ts): agent registration throws `DF0014` when a tool's `agent.description` is missing or empty.


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