Follow-up to #175.
Since `json_rpc_handler` was merged in #175, it has been removed from AGENTS.md.
The "Dependencies" section was also removed because the information there would have become redundant.
Consolidates four identical constructions of error `Tool::Response` in
`handle_call_tool_request` into a single private `error_tool_response` method,
reducing duplication and improving maintainability. No behavior change.
For example, the `title` introduced in #109 is not supported in the latest stable protocol version "2025-06-18":
https://modelcontextprotocol.io/specification/2025-06-18
It is supported in the Draft of the next version:
https://modelcontextprotocol.io/specification/draft
In other words, the fact that the Ruby SDK treats "2025-06-18" as the default protocol version while `title` is
only supported in the Draft results in an inconsistency.
Because of this, a new version `"Draft"` has been added to the list of supported versions.
Its value follows the schema below and is defined as `DRAFT-2025-v3`:
14ec41c/schema/draft/schema.ts (L15)
It was also considered to continue using the latest stable version "2025-06-18" as the Ruby SDK default instead of the Draft.
However, in that case, users would need to explicitly specify `MCP::Server.new(protocol_version: 'DRAFT-2025-v3')`,
which adds extra burden. In this PR, Draft is made the default in order to provide the following benefits:
- Users are likely to prefer using the Draft version over the latest stable version
- No need to specify the `protocol_version` option when initializing `MCP::Server`
- Users generally do not need to know the internal development value `DRAFT-2025-v3`
The primary case for specifying `protocol_version` explicitly is when strict adherence to a particular version is required.
However, it seems more practical to prioritize use cases where backward-compatible features, including those from the Draft,
are desirable. This is the rationale behind making the Draft version the default.
In addition, making the Draft version the default protocol version preserves backward compatibility for `MCP::Server`.
NOTE: `DRAFT-2025-v3` is a development code, so its value cannot be set externally.
It is applied either when `protocol_version` is omitted or when `nil` is set explicitly,
such as with `MCP::Configuration.new(protocol_version: nil)`.
This prevents users from creating implementations that depend on development codes like `DRAFT-2025-v3`.
`stateless` was supported in #101. However, as shown in the official specification below,
the supported transports are stdout and Streamable HTTP, and whether it is stateless is
a detail specific to Streamable HTTP:
https://modelcontextprotocol.io/specification/2025-06-18/basic/transports
This PR updates the documentation to describe `stateless` as part of the Streamable HTTP section.
- Create failing tests for `stateless` mode
- Implement `stateless` mode by turning of SSE in Streamable HTTP,
making the interaction a standard HTTP Req/Resp
README is generally better kept focused on information that is most valuable to users.
For that reason, release procedures that are not relevant to end users have been moved to
a separate RELEASE.md file.
Tool execution errors now return successful responses with isError: true
instead of JSON-RPC protocol errors, per the MCP specification.
This allows clients to distinguish between protocol-level errors and
tool execution errors, providing better error context.
Fixes#159
Update test_resources_returns_empty_array_when_no_resources to use
correct mock response format with empty resources array instead of
empty result object. Also reorder test to group with other resources
tests.
Follow up: https://github.com/modelcontextprotocol/ruby-sdk/pull/160
