manifest tools entries forbid inputSchema, so consumers that expect MCP's Tool shape reject the bundle

[shakaran]

The manifest schema rejects inputSchema inside a tools entry, allowing only name and description. A registry that consumes the declared tools as MCP Tool objects therefore cannot accept them, because Tool requires inputSchema.

This is not hypothetical: Smithery's publish endpoint answers 400 with Invalid input: expected object, received undefined, once per tool, for a bundle whose manifest passes mcpb validate. The result is that a bundle can declare tools that no consumer expecting the MCP shape can use, and declaring them costs a publish rather than gaining anything.

Reproduction

npx @anthropic-ai/mcpb@2.1.2 validate manifest.json with manifest_version 0.3:

"tools": [
  {
    "name": "example",
    "description": "An example tool",
    "inputSchema": { "type": "object", "properties": {}, "required": [] }
  }
]

ERROR: Manifest validation failed:
  - tools.0: Unrecognized key(s) in object: 'inputSchema'

Removing inputSchema validates and packs, and is then rejected downstream.

Question

Is the omission deliberate — tools being a display hint rather than a capability declaration — or should the entry allow the full Tool shape? If it is deliberate, saying so in MANIFEST.md would help, since the natural reading of a tools array is that it carries what tools/list returns.

Filed the mirror of this at arcadeai-labs/smithery-cli#806; the two schemas contradict each other and I have no view on which side should move.