docs: mention tool calling in sampling and retarget the sampling redirect #3030

Where was this agreed?

Requested by maintainer David Soria Parra as part of preparing the modelcontextprotocol.io documentation for the 2026-07-28 specification release.

Description

The 2026-07-28 spec release adds tool calling in sampling (tools/toolChoice). The client concepts Sampling section and the /docs/concepts/sampling redirect in docs.json predate this change.

Files to update:

• docs/docs/learn/client-concepts.mdx — mention tool-capable sampling in the Sampling section (ideally with the draft deprecation note)
• docs/docs.json — retarget the /docs/concepts/sampling redirect from the pre-tools 2025-06-18 spec to /specification/latest/client/sampling

Part of the 2026-07-28 release documentation tracking (milestone: 2026-07-28 Specification Release).