Tools tab: form rows for array-of-object inputs (currently JSON editor only) #2561

Which client?

Web

The problem

Tool inputs that are an array of objects — e.g. a list of line items — always render as a raw JSON editor in the Tools tab (SchemaForm sends any array that isn't a string-enum or const-option array to the JSON fallback). The editor gives no hint of the item shape: no field names, types, required fields or descriptions, although all of them are in the schema. You have to read the schema elsewhere to know what to type, and these list-shaped inputs are often a tool's most important argument.

Example input schema (as emitted by Rust schemars; Pydantic and reused Zod schemas produce the same $defs/$ref shape):

{
  "type": "object",
  "properties": {
    "email": { "type": "string" },
    "items": { "type": "array", "items": { "$ref": "#/$defs/Item" } }
  },
  "required": ["email", "items"],
  "$defs": {
    "Item": {
      "type": "object",
      "properties": {
        "sku": { "type": "string", "description": "Product SKU" },
        "quantity": { "type": "integer", "description": "Units to return" }
      },
      "required": ["sku", "quantity"]
    }
  }
}

Today items shows as an empty JSON editor. Seen on @modelcontextprotocol/inspector 2.8.0 (web), over both stdio and Streamable HTTP.

Solution you have in mind (optional)

Render an array whose items is an object schema (inline or via a local $ref) as a list of rows with add/remove, each row using the same indented sub-form SchemaForm already renders for nested objects — field labels, types, required markers and descriptions.

If a full row editor is too much for a first step, either of these would already help:

• show the resolved item schema (fields, types, required, descriptions) alongside the JSON editor, or
• pre-fill the editor with a template built from the item schema, e.g. [{"sku": "", "quantity": 0}].

Alternatives or workarounds you have tried

Hand-writing the JSON array after reading the input schema in the Protocol tab or in the server's source. It works, but it is slow and error-prone, especially for required nested fields.

Already built it locally?

No

Before you submit

• I searched existing issues and this is not a duplicate.
• This is a request for the Inspector itself, not for the MCP specification or an SDK.