modelcontextprotocol/java-sdk

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The official Java SDK for Model Context Protocol servers and clients. Maintained in collaboration with Spring AI

Stars: 3.7k
Forks: 1.1k
Open beginner issues: 0
Indexed issues: 113
Avg merge: 1d 15h
Merged PRs (30d): 9

Dominant language: Java
License: MIT
Last GitHub push: Sep 18, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue help wanted

Beginner friendly Everything

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113 issues indexed so far

Support parameter deserialisation to Java Objects using the MCPJsonMapper Open

waiting for triage

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/java-sdk#836 · 2 reactions · Opened Feb 25, 2026
API: Generalize notifications for SDK server classes Open

waiting for triage

Difficulty 5/5 Over a week Newbie friendliness 28/100

modelcontextprotocol/java-sdk#831 · Opened Feb 22, 2026
Deprecate old docs and add references to the new docs Open

documentation P2

Difficulty 2/5 1-3 hours Newbie friendliness 38/100

modelcontextprotocol/java-sdk#799 · 1 comment · Opened Feb 16, 2026
Add conformance score in README Open

documentation P2

Difficulty 2/5 1-3 hours Newbie friendliness 65/100

modelcontextprotocol/java-sdk#798 · 1 comment · Opened Feb 16, 2026
Migrate the reference & APIs docs to the java-sdk project Open

documentation P2

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#796 · Opened Feb 16, 2026
Support extensions SEP-2133 Open

area/client area/server enhancement P1

Difficulty 3/5 1-2 days Newbie friendliness 55/100

modelcontextprotocol/java-sdk#785 · 1 comment · Opened Feb 13, 2026
Feature Request: Support for MCP Apps Extension (UI capabilities) Open

enhancement waiting for triage

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/java-sdk#780 · 3 comments · Opened Feb 12, 2026
Introduce a unified Virtual Threads friendly API Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

modelcontextprotocol/java-sdk#778 · 1 comment · 19 reactions · Opened Feb 10, 2026
HttpClientStreamableHttpTransport: reconnect() called before status code check causes duplicate connections on 405 Open

waiting for user

Difficulty 3/5 1-2 days Newbie friendliness 75/100

modelcontextprotocol/java-sdk#773 · 2 comments · Opened Feb 5, 2026
Missing `@JsonIgnoreProperties(ignoreUnknown = true)` on capability sub-records Open

bug P1

Difficulty 2/5 1-3 hours Newbie friendliness 55/100

modelcontextprotocol/java-sdk#766 · 4 comments · Opened Jan 29, 2026
MCP server in WAR on application server Open

enhancement P3 waiting for user

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#763 · 5 comments · Opened Jan 29, 2026
StdioClientTransport: Inbound Scheduler and Error Scheduler threads are locked on Windows Open

bug P2

Difficulty 4/5 3-5 days Newbie friendliness 38/100

modelcontextprotocol/java-sdk#759 · 1 comment · Opened Jan 26, 2026
Add JPMS compatibility to Jackson JSON mapper Open

bug P2

Difficulty 2/5 1-3 hours Newbie friendliness 35/100

modelcontextprotocol/java-sdk#753 · Opened Jan 16, 2026
I would like to maintain MCP server state persisted (sessionId) Open

enhancement feature/session-storage P2

Difficulty 5/5 Over a week Newbie friendliness 42/100

modelcontextprotocol/java-sdk#738 · 2 comments · 3 reactions · Opened Dec 31, 2025
MCP server to be able to return custom http codes Open

enhancement feature/session-storage

Difficulty 3/5 1-2 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#737 · 1 comment · Opened Dec 31, 2025
Add ability to intercept tool call executions. Open

enhancement feature/repositories P3

Difficulty 4/5 3-5 days Newbie friendliness 25/100

modelcontextprotocol/java-sdk#720 · 8 comments · Opened Dec 12, 2025
Allow custom or numeric request ID generation (Snowflake MCP server rejects string IDs) Open

enhancement P3

Difficulty 4/5 3-5 days Newbie friendliness 38/100

modelcontextprotocol/java-sdk#703 · 1 comment · Opened Nov 27, 2025
Allow disabling `structuredContent` duplication in McpAsyncServer Open

enhancement P2

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#688 · 3 comments · Opened Nov 25, 2025
Java MCP Server examples are incomplete and non-runnable Open

documentation P3

Difficulty 3/5 1-2 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#687 · 2 comments · 3 reactions · Opened Nov 25, 2025
SDK rejects valid SSE comments, causing initialization timeout with Tavily MCP remote server Open

bug P2

Difficulty 3/5 1-2 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#685 · 1 comment · 3 reactions · Opened Nov 20, 2025
Extract McpAsyncClient and McpSyncClient as an interface Open

enhancement v2

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/java-sdk#680 · 1 comment · Opened Nov 19, 2025
SEP-1686: Tasks Support Open

enhancement P1

modelcontextprotocol/java-sdk#668 · 10 comments · 1 assignee · Opened Nov 15, 2025
There are two JsonSchemaValidator Open

enhancement P3

Difficulty 3/5 1-2 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#666 · 2 comments · Opened Nov 15, 2025
Null fields in JsonSchema without @Nullable annotation break serialization with Jackson Open

bug P3

Difficulty 3/5 1-2 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#664 · Opened Nov 12, 2025
Support running test cases in offline environments Open

enhancement P3 tests

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/java-sdk#636 · Opened Oct 27, 2025
Add timeout and fallback logging for closeGracefully() to prevent hanging shutdown Open

enhancement needs repro

Difficulty 4/5 3-5 days Newbie friendliness 50/100

modelcontextprotocol/java-sdk#635 · 1 comment · 1 reaction · Opened Oct 27, 2025
Add null-safety validation and safe fallbacks for features / clientCapabilities in McpAsyncClient constructor and feature branches Open

enhancement P3

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#634 · 1 reaction · Opened Oct 27, 2025
Allow dynamic generation of tool definition in MCP Server Open

enhancement feature/repositories

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#626 · 1 comment · Opened Oct 17, 2025
HttpClient resource leak causes thread accumulation and memory exhaustion Open

area/client area/transport bug

Difficulty 5/5 Over a week Newbie friendliness 38/100

modelcontextprotocol/java-sdk#620 · 3 comments · 1 reaction · Opened Oct 14, 2025
NullPointerException in McpClientSession Open

bug P2

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#605 · 4 comments · Opened Oct 7, 2025
jsonschemabuilder Open

enhancement needs confirmation waiting for user

Difficulty 5/5 Over a week Newbie friendliness 25/100

modelcontextprotocol/java-sdk#585 · Opened Sep 29, 2025
Refactor McpTransport Abs ,Reduce duplicate code and improve readability Open

enhancement P3

Difficulty 4/5 3-5 days Newbie friendliness 25/100

modelcontextprotocol/java-sdk#581 · 1 comment · Opened Sep 28, 2025
Add Primitive repository APIs (`ResourceRepository`, `ToolsRepository`, ... ) Open

enhancement feature/repositories P3

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/java-sdk#578 · 20 comments · 1 reaction · Opened Sep 26, 2025
Simplify error response when accessing MCP without session ID Open

enhancement waiting for triage

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

modelcontextprotocol/java-sdk#577 · 3 comments · Opened Sep 26, 2025
MCP_SESSION_ID is improperly named Open

bug needs confirmation

Difficulty 2/5 1-3 hours Newbie friendliness 25/100

modelcontextprotocol/java-sdk#563 · 3 comments · Opened Sep 20, 2025
Add an ability to trace requests Open

enhancement P3

Difficulty 4/5 3-5 days Newbie friendliness 38/100

modelcontextprotocol/java-sdk#561 · 6 comments · Opened Sep 19, 2025
DefaultMcpTransportSession#closeGracefully leaks resources on incomplete DELETE response Open

bug P2

modelcontextprotocol/java-sdk#547 · 6 comments · 1 assignee · Opened Sep 11, 2025
[HTTP+SSE] Throw the Initialization Exception Immediately for Invalid SSE Endpoint Instead of After Timeout Open

bug P2

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#546 · 1 comment · Opened Sep 11, 2025
MCP Registry Open

enhancement needs confirmation

modelcontextprotocol/java-sdk#545 · 1 comment · 1 assignee · Opened Sep 11, 2025
add a configuration option that can ignore illegal format jsonrpc Open

enhancement P3

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#544 · 1 comment · 1 reaction · Opened Sep 10, 2025
Streamable Stateless server should support upgrade to SSE response Open

feature/stateless-sse-upgrade

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#539 · 3 comments · Opened Sep 6, 2025
Resource templates should support handlers Open

enhancement feature/repositories P2

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/java-sdk#534 · 1 comment · Opened Sep 4, 2025
[HELP NEEDED] io.modelcontextprotocol.spec.McpError: Client failed to initialize by explicit API call Open

question

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#501 · 8 comments · 1 reaction · Opened Aug 18, 2025
Current implementation of HttpServletStreamableServerTransportProvider or HttpServletSseServerTransportProvider needs strict stickyness Open

enhancement feature/session-storage P2

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/java-sdk#499 · 11 comments · Opened Aug 18, 2025
io.modelcontextprotocol.client.transport.StdioClientTransport#closeGracefully Open

area/client enhancement P2 ready for work

Difficulty 3/5 1-2 days Newbie friendliness 55/100

modelcontextprotocol/java-sdk#496 · 2 comments · Opened Aug 15, 2025
Should McpTransportContextExtractor contain default methods for protocol version, lastEventId and sessionId Open

waiting for triage

Difficulty 3/5 1-2 days Newbie friendliness 45/100

modelcontextprotocol/java-sdk#492 · Opened Aug 14, 2025
Publish a `mcp-annotations` module with just annotations for MCP Server primitives annotations. Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/java-sdk#491 · 6 comments · 2 reactions · Opened Aug 14, 2025
Bad assertion in testCallTool Open

needs confirmation P3 tests

Difficulty 2/5 1-3 hours Newbie friendliness 75/100

modelcontextprotocol/java-sdk#464 · 2 comments · Opened Aug 7, 2025
Support Unix Domain Sockets as local-only transport Open

enhancement waiting for triage

Difficulty 4/5 3-5 days Newbie friendliness 25/100

modelcontextprotocol/java-sdk#415 · 3 comments · 2 reactions · Opened Jul 19, 2025
Resolve message endpoint path using request context path Open

area/server enhancement P2

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

modelcontextprotocol/java-sdk#400 · 3 comments · 1 reaction · Opened Jul 15, 2025

modelcontextprotocol/java-sdk

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