addMcpServer
A Claude Code settings key, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Headless SDK sessions expose a session object for MCP servers with addMcpServer, removeMcpServer, toast, status and refreshContext.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.259.
In the changelogs
3Releases whose published page names addMcpServer.
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v2.1.281
Removing an MCP server now cancels a pending add of the same server
Removing an MCP server while it is still being added now cancels the add, so it does not reappear
found in this entry's text, named in this entry
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v2.1.260
Plugin
$.tool.registernow bounds MCP server connect timePlugin tool registration now times out instead of hanging on a slow MCP server connect.
found in this entry's text
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v2.1.259
Headless SDK sessions expose a bindable
$.tool.registerAPI for MCP serversHeadless SDK sessions expose a session object for MCP servers with addMcpServer, removeMcpServer, toast, status and refreshContext.
found in this entry's text, named in this entry
First cited
1The earliest release whose published evidence quoted addMcpServer was v2.1.260, 3 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the settings key does. All settings keys.