stacklok / toolhive / 19136370073

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Support MCP servers with partial capabilities in vmcp (#2416)

The vmcp was rejecting backends that don't implement all three MCP
capabilities (tools, resources, prompts). This violated the MCP
specification, which explicitly makes all capabilities optional.

The oci-registry MCP server only implements tools, causing vmcp to
fail during aggregation when it tried to unconditionally query
resources and prompts.

Changes:
- Query server capabilities during MCP initialization handshake
- Conditionally query only advertised capabilities
- Return empty results for unsupported capabilities
- Add tests for backends with partial capability support

This allows vmcp to successfully aggregate backends that implement
any subset of tools, resources, and prompts, as intended by the
MCP specification.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

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