Update `tool.Invoke()` to return type `any` instead of `[]any`.
Toolbox return a map with the `results` key, and the SDK reads the
string from the key. So this won't break existing SDK implementation.
Fixes#870
This PR refactors the tool configuration and loading mechanism to use a
dynamic registration pattern. Each tool package now registers itself
with a central registry, and the server configuration code uses this
registry to decode and initialize tools.
Key changes:
- Introduced tools.Register and tools.DecodeToolConfig for dynamic tool
handling.
- Removed direct imports of specific tool packages from
internal/server/config.go.
- Updated individual tool packages to include init() functions for
self-registration.
- Modified ToolKind constants to be local kind constants within each
tool package.
- Adjusted test files to reflect the changes in tool kind identifiers.
This change simplifies adding new tools and decouples the server
configuration from specific tool implementations.
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Co-authored-by: Yuan Teoh <yuanteoh@google.com>
Co-authored-by: Yuan <45984206+Yuan325@users.noreply.github.com>
