Card-to-card linking, now available as an MCP tool

Agents can now link cards to other cards through the Simple Product MCP. Three new tools are live on the connector:

• link_card_to_card — create a link between two cards
• unlink_card_from_card — remove a link between two cards
• get_linked_cards — list every card linked to a given card (both directions)

Why this exists

The MCP already had link_doc_to_doc for connecting docs to each other, but no equivalent for cards — even though the underlying cardLinks schema and the "Related Cards" section in the card panel UI already used it. If you were working with an agent and wanted it to wire up "this bug blocks this feature" or "this card is a follow-up to that one," you had to open the app to make the connection manually.

Now the whole trio is symmetric with docs, and same-type card relationships are fully reachable from agent workflows.

When to use it

• Block/blocked-by relationships — "this task depends on that one"
• Follow-up work — a bug fix card linking back to the epic that discovered it
• Related epics — cards on different boards that ship together

Bonus: workspace switching now sticks

We also fixed a related bug: switch_workspace was silently reverting on the next tool call for MCP clients that don't preserve session headers across requests — most notably Claude mobile and web connectors. If you tried to switch to a different workspace from your phone and your next tool call still returned the wrong workspace's data, that was this bug. It's fixed. switch_workspace(persistAsDefault: true) now actually persists.

Ship path

Both changes are server-side and picked up the moment you restart or reconnect your MCP client.