[fuseraft]

Why

When two MCP servers expose a tool with the same name, every request fails with a 400: tools: Tool names must be unique. The same happens when a server's tool shares a name with a built-in one, such as read_file. #219 makes this likelier: a server the launcher provides and one you saved can be the same server under different names. I hit it while testing the VS Code MCP view.

What

• McpToolNames.Disambiguate: an MCP tool whose name another tool also has is offered as <server>_<tool>, such as Sql_query_database.
  • Built-in tools always keep their names, so @mentions and other code that looks tools up by name still finds them.
  • Characters a tool name can't hold are replaced with _. Names stay within 64 characters, and a name that's already taken gets _2.
• The rename is a DelegatingAIFunction that changes only the name. Calls, schema and GetService go to the server's own tool, so REPL approval gates and read-only hints still apply.
• Applied where tool lists reach a model:
  • the REPL's GetActiveTools, which also feeds ChatOptions;
  • each orchestration agent's tools (ConvertPluginTools);
  • a subagent's custom SubagentPlugins.
• Docs: a note in docs/mcp.md.

Also: the build's three warnings

The build now has none.

• CS4014 in ReplTurn: the auto-title task (ReplAutoTitle.MaybeStart) runs alongside the next prompt on purpose and handles its own errors. It's discarded explicitly (_ =) instead of awaited, so behavior doesn't change.
• CA2022 in SseEventIdleTimeoutStreamTests: the byte-idle test expects the read to throw, so it uses ReadExactlyAsync instead of ignoring ReadAsync's count. It still goes through the stream's ReadAsync(Memory<byte>).
• CS8619 in McpSessionManagerStderrTests: the env helper now takes Dictionary<string, string?>, matching McpServerConfig.Env.

Testing

• McpToolNamesTests:
  • no clash returns the same instances;
  • a server-vs-server clash and a server-vs-built-in clash;
  • a renamed tool invokes its own tool and still answers GetService;
  • unsafe server names, taken names and long names.
• AgentToolResolverTests covers an agent's tools and a subagent's tools. ReplCommandsMcpServerLifecycleTests covers GetActiveTools and ChatOptions. Each fails if its wiring is removed.
• Live test, a bridge chat with the same sql-mcp connected twice (saved and launcher-provided):
  • The model saw Local_list_databases and Sql_list_databases.
  • It called Sql_list_databases and got the server's answer, where before every turn failed.

/mcp still lists each server's tools under their own names.