bug: json schema generated is incorrect

[JosiahParry]

The tools/list from my MCP server is generating the following output. For of them are generating properties":[] which should instead be properties: {}.

{"jsonrpc":"2.0","result":{"tools":[{"name":"add_todo","description":"Create a new todo item","inputSchema":{"type":"object","properties":{"title":{"type":"string","title":"Title","description":"The todo title"},"description":{"type":"string","title":"Description","description":"Detailed description of the todo"},"deadline":{"type":"string","title":"Deadline","description":"Deadline as ISO 8601 date string (e.g., '2026-01-15')"},"priority":{"type":"number","title":"Priority","description":"Priority level from 1 (lowest) to 5 (highest)"},"tags":{"type":"array","title":"Tags","description":"List of tags for categorization","items":{"type":"string","title":"Tag","description":"A tag string"}},"category":{"type":"string","title":"Category","description":"Category ID (ULID) for the todo"}},"additionalProperties":false,"required":["title"]}},{"name":"get_todo","description":"Retrieve a specific todo by ID","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the todo to retrieve"}},"additionalProperties":false,"required":["id"]}},{"name":"update_todo","description":"Update fields of an existing todo","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the todo to update"},"title":{"type":"string","title":"Title","description":"New title for the todo"},"description":{"type":"string","title":"Description","description":"New description"},"deadline":{"type":"string","title":"Deadline","description":"New deadline as ISO 8601 date string"},"priority":{"type":"number","title":"Priority","description":"New priority level (1-5)"},"tags":{"type":"array","title":"Tags","description":"New list of tags","items":{"type":"string","title":"Tag","description":"A tag string"}},"category":{"type":"string","title":"Category","description":"New category ID"}},"additionalProperties":false,"required":["id"]}},{"name":"delete_todo","description":"Delete a todo by ID","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the todo to delete"}},"additionalProperties":false,"required":["id"]}},{"name":"mark_complete","description":"Mark a todo as completed","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the todo to mark complete"}},"additionalProperties":false,"required":["id"]}},{"name":"list_all","description":"List all todos (completed and incomplete)","inputSchema":{"type":"object","properties":[],"additionalProperties":false}},{"name":"list_incomplete","description":"List all incomplete todos","inputSchema":{"type":"object","properties":[],"additionalProperties":false}},{"name":"list_completed","description":"List all completed todos","inputSchema":{"type":"object","properties":[],"additionalProperties":false}},{"name":"add_category","description":"Create a new category","inputSchema":{"type":"object","properties":{"title":{"type":"string","title":"Title","description":"The category title"},"description":{"type":"string","title":"Description","description":"Description of the category"}},"additionalProperties":false,"required":["title"]}},{"name":"get_category","description":"Retrieve a specific category by ID","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the category to retrieve"}},"additionalProperties":false,"required":["id"]}},{"name":"update_category","description":"Update fields of an existing category","inputSchema":{"type":"object","properties":{"id":{"type":"string","title":"ID","description":"The ULID of the category to update"},"title":{"type":"string","title":"Title","description":"New title for the category"},"description":{"type":"string","title":"Description","description":"New description"}},"additionalProperties":false,"required":["id"]}},{"name":"list_categories","description":"List all categories","inputSchema":{"type":"object","properties":[],"additionalProperties":false}}]},"id":1}

This results in an error from claude mcp integration

2026-01-13T00:00:30.963Z [DEBUG] MCP server "chief": Successfully connected to http server in 342ms
2026-01-13T00:00:30.963Z [DEBUG] MCP server "chief": Connection established with capabilities: {"hasTools":true,"hasPrompts":true,"hasResources":true,"serverVersion":{"name":"Chief Portfolio Server","version":"0.0.0.9000"}}
2026-01-13T00:00:30.967Z [DEBUG] MCP server "chief": No token data found
2026-01-13T00:00:30.967Z [DEBUG] MCP server "chief": No token data found
2026-01-13T00:00:30.967Z [DEBUG] MCP server "chief": No token data found
2026-01-13T00:00:30.973Z [ERROR] MCP server "chief" Failed to fetch tools: [
  {
    "expected": "record",
    "code": "invalid_type",
    "path": [
      "tools",
      5,
      "inputSchema",
      "properties"
    ],
    "message": "Invalid input: expected record, received array"
  },
  {
    "expected": "record",
    "code": "invalid_type",
    "path": [
      "tools",
      6,
      "inputSchema",
      "properties"
    ],
    "message": "Invalid input: expected record, received array"
  },
  {
    "expected": "record",
    "code": "invalid_type",
    "path": [
      "tools",
      7,
      "inputSchema",
      "properties"
    ],
    "message": "Invalid input: expected record, received array"
  },
  {
    "expected": "record",
    "code": "invalid_type",
    "path": [
      "tools",
      11,
      "inputSchema",
      "properties"
    ],
    "message": "Invalid input: expected record, received array"
  }
]

I believe i can fix this by updating the properties correctly in my MCP server, but it would be great if this was caught by mcpr

[JosiahParry]

I believe this is actually a bug from {yyjsonr} see coolbutuseless/yyjsonr#52

Note the fix is to use setNames(list(), character())