DF0043: Invalid RPC Argument

Message

RPC function "{name}" received an invalid argument at position {index}: {issues}

Cause

Each declared args schema validates its argument before the handler runs, on every path: local, over-the-wire, and the agent/MCP bridge. The argument at {index} failed its schema. Validation guards without rewriting, so unmentioned object fields still reach the handler.

Example

const greet = defineRpcFunction({
  name: 'greet',
  args: [v.string()],
  returns: v.string(),
  handler: name => `hi ${name}`,
})

// ✓ Good
await ctx.rpc.functions.greet('ada')

// ✗ Bad: a number where a string is required → DF0043 at position 0
await ctx.rpc.functions.greet(42 as never)

Fix

Pass a value that satisfies the args schema declared for the function, or widen the schema if the value is legitimately allowed.

Source

• packages/devframe/src/rpc/validate-io.ts: validateRpcArgs() throws DF0043 on the first argument that fails its declared schema.