fix: Add required 'type' field to MCP tool responses and remove unsupported version argument

[ddonghi]

Summary

This PR fixes two critical bugs that prevented all tools from working correctly:

1. Missing type field in TextContent responses - All tool responses were missing the required type field, causing Pydantic validation errors
2. Unsupported version argument - FastMCP.__init__() was called with a version argument that doesn't exist in the current MCP library

Bug #1: Missing 'type' field in TextContent responses

Error Message

Error executing tool list_clusters: 1 validation error for list_clustersOutput
result.0.type
  Field required [type=missing, input_value={'text': '{"clusters": [...'}, input_type=dict]

Root Cause

All tools returned [{"text": json.dumps(result)}] but the MCP TextContent specification requires [{"type": "text", "text": json.dumps(result)}].

Affected Tools (All 11 tools)

• list_clusters
• create_cluster
• terminate_cluster
• get_cluster
• start_cluster
• list_jobs
• run_job
• list_notebooks
• export_notebook
• list_files
• execute_sql

Bug #2: Unsupported version argument

Error Message

TypeError: FastMCP.__init__() got an unexpected keyword argument 'version'

Root Cause

Line 37 in src/server/databricks_mcp_server.py passed version="1.0.0" and instructions to FastMCP.__init__(), but these arguments are not supported in the current version of the mcp library.

Changes Made

1. Line 37-39: Removed version and instructions arguments from FastMCP.__init__()
2. All return statements (22 occurrences): Added "type": "text" to all response dictionaries

Example Fix

- return [{"text": json.dumps(result)}]
+ return [{"type": "text", "text": json.dumps(result)}]

Testing

After applying these fixes, all tools work correctly:

• ✅ list_clusters - Returns cluster information
• ✅ list_notebooks - Returns workspace notebooks
• ✅ list_files - Returns DBFS file listings
• ✅ All other tools function as expected

Tested with:

• mcp library version: 1.27.0
• Python: 3.13.2
• MCP Client: Claude Code

Additional Context

The MCP specification requires all TextContent objects to have a type field. See: https://modelcontextprotocol.io/

The FastMCP class in the current mcp library doesn't support version or instructions arguments in its __init__() method.