Currently, MCP has three versions: 2024-11-05, 2025-03-26, and 2025-06-18.
- https://modelcontextprotocol.io/specification/2024-11-05/basic/transports (stdio and HTTP with SSE)
- https://modelcontextprotocol.io/specification/2025-03-26/basic/transports (stdio and Streamable HTTP)
- https://modelcontextprotocol.io/specification/2025-06-18/basic/transports (stdio and Streamable HTTP)
The newer specification supports stdio and Streamable HTTP as transport mechanisms.
Only the oldest version, 2024-11-05, supports stdin and HTTP with SSE,
but that version is now considered legacy.
Given the current behavior of the Ruby SDK, it likely makes more sense to set
the default protocol version to the latest one, 2025-06-18, rather than the oldest, 2024-11-05.
Ideally, the implementation should adjust its behavior based on the version,
but this PR is limited to updating the default protocol version only.
## Motivation and Context
Currently, MCP supports the following three protocol versions:
"2025-06-18", "2025-03-26", and "2024-11-05".
https://modelcontextprotocol.io/introduction
As shown in the changes to `test/mcp/configuration_test.rb`,
the `protocol_version` value is not currently being validated,
which allows unexpected `protocol_version` values to be accepted.
This PR ensures that only supported protocol versions are accepted.
## How Has This Been Tested?
Existing tests have been updated and new tests have been added.
## Breaking Changes
None. If it becomes an issue, it means a value that was not originally intended has been used.
## Additional context
While one possible approach might be to fall back to a default protocol version
when an invalid `protocol_version` value is provided,
this PR opts to reject invalid `protocol_version` values explicitly.
The reasoning is that encouraging users to provide intentional,
valid input is preferable to silently falling back to a default,
which could lead to unexpected behavior.
The reason for the change is that a NameError occurs when a POST request is made while the stream is closed because ModelContextProtocol is undefined.
I have also added test cases to check the behaviour when IOError and Errno::EPIPE occurs.
- Updated `call` method in `MCP::Tool` and `MCP::Prompt` to accept `server_context` as an optional parameter.
- Refactored `MCP::Server` to streamline argument handling for tool and prompt calls, introducing helper methods `call_tool_with_args` and `call_prompt_template_with_args`.
- Adjusted tests to reflect changes in method signatures and ensure compatibility with optional `server_context` parameter.
Refactor capabilities handling into MCP::Server::Capabilities to improve
code organization and separation of concerns. This provides a cleaner API
for configuring server capabilities including prompts, resources, tools,
completions, logging, and experimental features.
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
Follow-up to #27.
This PR fixes the following build error:
```console
$ bundle exec rake
/Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'Kernel.require': cannot load such file -- mcp/transports/stdio (LoadError)
Did you mean? mcp/transports/stdio_transport_test
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'block (2 levels) in Kernel#replace_require'
from /Users/koic/src/github.com/modelcontextprotocol/ruby-sdk/test/mcp/transports/stdio_transport_test.rb:4:in '<top (required)>'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'Kernel.require'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/3.5.0+1/bundled_gems.rb:59:in 'block (2 levels) in Kernel#replace_require'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:21:in 'block in <main>'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:6:in 'Array#select'
from /Users/koic/.rbenv/versions/3.5-dev/lib/ruby/gems/3.5.0+1/gems/rake-13.3.0/lib/rake/rake_test_loader.rb:6:in '<main>'
rake aborted!
Command failed with status (1)
/Users/koic/.rbenv/versions/3.5-dev/bin/bundle:25:in 'Kernel#load'
/Users/koic/.rbenv/versions/3.5-dev/bin/bundle:25:in '<main>'
Tasks: TOP => default => test
(See full trace by running task with --trace)
```
https://github.com/modelcontextprotocol/ruby-sdk/actions/runs/15428236624/job/43420346011
The following is stated in #27.
> Breaking Changes
> `MCP::Transports::StdioTransport` is now `MCP::Server::Transports::StdioTransport`
What is shown here is the new name `MCP::Server::Transports::StdioTransport`, not `MCP::Server::Transports::Stdio`.
Therefore, the file path has been updated from `lib/mcp/server/transports/stdio.rb` to `lib/mcp/server/transports/stdio_transport.rb` to
match the module name. If `MCP::Server::Transports::Stdio` is preferred instead, please let me know and I will open a separate PR.
Based on the following information, `rubocop-minitest` and `rubocop-rake` have been added
for development. Autocorrection has been applied for offenses detected by `rubocop-minitest`.
```console
$ bundle exec rake
(snip)
Running RuboCop...
Inspecting 40 files
........................................
40 files inspected, no offenses detected
Tip: Based on detected gems, the following RuboCop extension libraries might be helpful:
* rubocop-minitest (https://rubygems.org/gems/rubocop-minitest)
* rubocop-rake (https://rubygems.org/gems/rubocop-rake)
You can opt out of this message by adding the following to your config
(see https://docs.rubocop.org/rubocop/extensions.html#extension-suggestions for more options):
AllCops:
SuggestExtensions: false
```
If preserving the existing behavior is preferred, it is also possible to set `SuggestExtensions: false`.
This PR fixes incorrect capabilities handling for `completion/complete`.
As specified, the capability of `completion/complete` is `completions`, not `prompts`:
https://modelcontextprotocol.io/specification/2025-03-26/server/utilities/completion#capabilities
Note that in the Ruby SDK, `completion/complete`, like `logging/setLevel`, is not yet implemented.
Therefore, an empty implementation has been added to server.rb.
- add support for resource templates
- improve capability negotiation on handlers
- clean up readme
- reduce default protocol version to "2024-11-05"
- address spec compliance of resources
- add debug gem to development
- alias ModelContextProtocol to MCP
- move prompt subclasses to subdir
- improve tool and prompt definition
- improve passing of server context to tools
- improve tool input schema validation
- Allow protocol version to be set at the server level through configuration instead of a class method, providing more flexibility in protocol version management [#43](https://github.com/Shopify/mcp-ruby/pull/43) @topherbullock
- Fixed instrumentation handling to ensure accurate timing information and proper error reporting [#42](https://github.com/Shopify/mcp-ruby/pull/42) @tobiasbales
- Improved error handling and reporting in the server
- Fixed timing information collection in instrumentation
- Added proper error types for different failure scenarios
- Enhanced test coverage for error cases
- [Allow protocol version to be set at the server level #43](https://github.com/Shopify/mcp-ruby/pull/43) @topherbullock
- [Fix instrumentation handling #42](https://github.com/Shopify/mcp-ruby/pull/42) @tobiasbales
Bump protocol version to 2025-03-26
Provide fallback value for tool_name
Make configuration per server
Add support for tool annotations
document tool annotations
- Added support for handle_json method from JSON RPC gem to allow consumers to pass JSON strings
- Added context parameter to prompt templating system
- Updated tool and prompt registration to use class references instead of instances
- Changed tool response is_error to isError to match protocol specification
