v7.1.2

[7.1.2] - 2026-09-25

Added

• mcpServer.instructions — an optional string returned as initialize.result.instructions. Claude Code adds it to the system prompt of every session; Cursor writes it to mcps/<server>/INSTRUCTIONS.md.
• MCP protocol version negotiation: initialize now echoes a client's 2025-06-18 or 2024-11-05 protocolVersion, and answers 2025-06-18 (the newest) when the request omits it or asks for an unsupported version. Previously the server always claimed 2024-11-05 regardless of what the client sent or what fields it actually returned. tools/list's outputSchema and tools/call's structuredContent — both defined starting in 2025-06-18 — are now only sent for sessions that negotiated that version or later; a 2024-11-05 session no longer receives fields from a spec revision it never agreed to.
• mcpSizeReport(root) and mcpServer.sizeLimits — measures every MCP tool's description length and pretty-printed definition (bytes and lines) against configurable limits approximating two real client behaviors (Claude Code truncates long tool descriptions; Cursor reads each tool's synced definition file in bounded chunks), and returns warnings for anything over. serveMcp runs this at startup and writes warnings to stderr before the "MCP ready" line; docs mcp now includes a ## Tool sizes table. Set any limit to false to disable that check.
• mcpTool.notes (string | false) — overrides a leaf's notes in the MCP tool description only; CLI --help continues to show the leaf's own notes unchanged. Useful for a note that only makes sense with --help in front of it, or to keep a tool's definition under a size limit.

Changed

• Discriminated anyOf/oneOf unions (every branch has a properties key with a string const or all-string enum, and the value sets are disjoint) now report only the branch matching the instance's discriminator value, instead of every branch's unrelated errors at once. A missing, non-string, or unmapped discriminator value collapses to one synthetic message naming the valid choices. Non-discriminated unions are unaffected. Along the way, two cfworker @cfworker/json-schema quirks are also cleaned up for every validated schema (not just discriminated unions): a spurious additionalProperties + "False boolean schema." pair it emits even for a property that's genuinely declared in properties, and dropping now-redundant wrapper errors ($ref, properties, items, anyOf, oneOf, …) once a more specific error survives underneath them. Discriminator detection also resolves each branch through $ref before inspecting its properties — schema generators such as ts-json-schema-generator write every anyOf branch as a bare { $ref } into definitions rather than inlining it, which previously made every branch look property-less and silently fell back to the noisy full-error listing.