Issues

• Lost-response retry on a mutating tools/call re-executes external effects — reproduction evidence and a spec-clarification question

  modelcontextprotocol/modelcontextprotocol#3394 · Filter by author arjun2075 opened on Sep 27, 2026
  8

• Origin validation rejects browser-based MCP clients on authenticated remote servers

  bug
  modelcontextprotocol/modelcontextprotocol#3370 · Filter by author daoluc opened on Sep 18, 2026
  6

• Security considerations section can be improved

  bug
  modelcontextprotocol/modelcontextprotocol#3361 · Filter by author loganaden opened on Sep 14, 2026
  1

• cancellation.mdx and subscriptions.mdx disagree on how a server ends a subscriptions/listen stream

  modelcontextprotocol/modelcontextprotocol#3348 · Filter by author AmirK-S opened on Sep 6, 2026
  1

• inputSchema and requestedSchema hard-code JSON Schema keywords into dialect-agnostic slots

  bug
  modelcontextprotocol/modelcontextprotocol#3238 · Filter by author clemensv opened on Aug 14, 2026
  1

• Tasks extension (SEP-2663): no interoperable surface for partial output of a running task

  modelcontextprotocol/modelcontextprotocol#3237 · Filter by author Cam10001110101 opened on Aug 14, 2026

• Clarify whether notifications/resources/list_changed should be sent if the list of resource templates changes

  bug
  modelcontextprotocol/modelcontextprotocol#3226 · Filter by author mkouba opened on Aug 11, 2026

• MCP-2026-015: server/discover instructions field enables prompt injection (amplified by cacheScope:public)

  modelcontextprotocol/modelcontextprotocol#3213 · Filter by author shunfeng8421 opened on Aug 7, 2026
  9

• MCP-2026-008: CacheableResult cacheScope:public enables cross-user cache poisoning

  modelcontextprotocol/modelcontextprotocol#3207 · Filter by author shunfeng8421 opened on Aug 6, 2026
  2

• generate:schema:json produces empty schemas when using wildcard type on Windows

  bug
  modelcontextprotocol/modelcontextprotocol#3114 · Filter by author vortsghost2025 opened on Jul 22, 2026

• [Spec Gap] Tool Execution Errors lack a schema-governed signal for LLM forwarding — structuredContent should be defined for error path

  bug
  modelcontextprotocol/modelcontextprotocol#3003 · Filter by author antara1414 opened on Jul 2, 2026
  10

• SEP-2549: clarify whether cacheScope is required or defaults to public

  bug
  modelcontextprotocol/modelcontextprotocol#2939 · Filter by author DaleSeo opened on Jun 18, 2026
  

• MCP protocol lacks a mechanism for tools to stream incremental results

  modelcontextprotocol/modelcontextprotocol#2932 · Filter by author fy2ne opened on Jun 16, 2026
  9

• MRTR url-mode: standardize the "still waiting" response (state-only InputRequiredResult) + retry/cancel guidance

  modelcontextprotocol/modelcontextprotocol#2920 · Filter by author ferentinai opened on Jun 15, 2026

• MRTR: inputRequests is a closed enum of three methods — add an extensible / reverse-DNS-namespaced member type

  modelcontextprotocol/modelcontextprotocol#2919 · Filter by author ferentinai opened on Jun 15, 2026
  2

• SDK feedback: oneOf in tool inputSchema isn't practically consumable by tool-calling LLMs

  modelcontextprotocol/modelcontextprotocol#2806 · Filter by author hypeprinter007-stack opened on May 27, 2026
  1

  

• SEP-2352 Clarification

  documentationsdk/2026-07-feedback
  modelcontextprotocol/modelcontextprotocol#2748 · Filter by author guglielmo-san opened on May 19, 2026
  2

• No visibility of errors from tool call responses

  bug
  modelcontextprotocol/modelcontextprotocol#2734 · Filter by author rlb567 opened on May 16, 2026
  8

• Clarify behavior when initialize.params.protocolVersion conflicts with MCP-Protocol-Version

  bug
  modelcontextprotocol/modelcontextprotocol#2721 · Filter by author cclabadmin opened on May 13, 2026

• Schema generation pipeline may produce overly permissive schemas without safeguards

  bug
  modelcontextprotocol/modelcontextprotocol#2600 · Filter by author httpsVishu opened on Apr 18, 2026
  2

• SDK Tiering - 'Task' issues should be out of scope for triage SLAs

  modelcontextprotocol/modelcontextprotocol#2518 · Filter by author jeffhandley opened on Apr 4, 2026

• Provide guidance on how to set/use server description/instructions

  documentationenhancement
  modelcontextprotocol/modelcontextprotocol#2146 · Filter by author lirc572 opened on Jan 24, 2026
  2

  

• Unnecessary Request and Notification objects

  bug
  modelcontextprotocol/modelcontextprotocol#2126 · Filter by author Kludex opened on Jan 21, 2026
  2

• Add server instructions documentation to main docs

  documentationenhancement
  modelcontextprotocol/modelcontextprotocol#2060 · Filter by author olaservo opened on Jan 7, 2026
  1

• Register docs MCP server in the official MCP Registry

  documentation
  modelcontextprotocol/modelcontextprotocol#2046 · Filter by author olaservo opened on Jan 4, 2026