Tool annotations use invalid `idempotentHint` field

[bryan-anthropic]

Hi from Anthropic!

The tool annotations in src/tools/ use idempotentHint, which is not a recognized field in the MCP Tool Annotations specification. Claude Desktop ignores unrecognized fields, so these tools are effectively unannotated.

All four tools (get-data, get-schema, list-dataflows, get-dataflow) are read-only data fetchers and should use readOnlyHint: true instead. Additionally, get-dataflow is missing any hint entirely.