MCP Fusion
AI-First DX for the Model Context Protocol.

Type Alias: PromptParamDef ​

ts
type PromptParamDef = 
  | "string"
  | "number"
  | "boolean"
  | StringParamDef
  | NumberParamDef
  | BooleanParamDef
| EnumParamDef<string>;

Defined in: packages/core/src/prompt/types.ts:300

Prompt-safe param descriptors: only flat primitives allowed.

Why? MCP clients (Claude Desktop, Cursor) render prompt arguments as native visual forms. Nested objects and arrays cannot be rendered by any current MCP client — allowing them produces invisible or broken form fields.

Allowed: 'string', 'number', 'boolean', StringParamDef, NumberParamDef, BooleanParamDef, EnumParamDef.

❌ ArrayParamDef — cannot be rendered as a form field. ❌ Nested ZodObject — cannot be rendered as a form field.

See ​

PromptParamsMap for the full prompt args type