Add read/write mode definition to tools

[edwardcqian]

Currently there's no good way to avoid using tools that can persist changes.

Adding the notion of mode to separate the "read" tools from the "write" tools.

Notes for reviewers:

• Not sure if read or write is the best terms here, open to suggestions
• Sift tools are a bit tricky, since error pattern and slow request technically creates an investigation

[edwardcqian]

Ah, just realized there's the readOnly annotation 🤦