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Changelog

Source: NEWS.md

mcplite 0.2.0

CRAN release: 2026-10-20

  • Adds stateless MCP 2026-07-28 support while retaining initialize-based MCP 2024-11-05, 2025-06-18, and 2025-11-25. Modern discovery, tool listing, and tool calls work without initialization; legacy ping behavior is preserved, while modern ping is unsupported.
  • Adds server/discover with deterministic four-version ordering. Successful modern results include canonical server identity and resultType = "complete"; discovery and tool-list results include public cache hints.
  • Expands tool schemas and protocol-native results. Complete object-root input schemas retain JSON Schema 2020-12 keywords; modern clients can receive supported output-schema roots and all JSON structured-content shapes, while older protocols receive compatible projections and fallback content.
  • Adds payload options mcplite.json.null, mcplite.json.na, and mcplite.json.auto_unbox, preserving published defaults and fixed protocol and metadata encoding. See help("mcplite-results") for configuration details.
  • Restores empty structured-root lists as {} and removes the unreleased scalar-NA coercion in favor of jsonlite’s class-specific mappings.

mcplite 0.1.0

CRAN release: 2026-08-03

  • First release of the lightweight, tools-only Model Context Protocol (MCP) server over standard input and output (stdio), supporting the MCP lifecycle, ping, tools/list, and tools/call.
  • Supports protocol versions 2024-11-05, 2025-06-18, and 2025-11-25.
  • Provides native tool and JSON Schema helpers, with optional interoperability for compatible ellmer tool definitions.
  • Adds explicit protocol-native tool results through tool_result() and the content_text(), content_image(), content_audio(), content_resource_link(), and content_resource() constructors. Results may contain ordered mixed content, structured content, annotations, and metadata while ordinary R return values retain their existing text conversion.
  • Adds object-shaped output_schema support to tool(). Tool definitions and results follow the negotiated MCP version: structured output, output schemas, audio, resource links, and content metadata are available for 2025-06-18 and later, with compatible fallback or contained tool errors for 2024-11-05.
  • Handles protocol negotiation, request validation, JSON-RPC errors, and MCP tool-call errors while keeping the stdio protocol stream usable.
  • Automatically traces every envelope-valid MCP operation with one OpenTelemetry server span, while keeping tool-authored child spans optional. Standard otel and otelsdk configuration owns provider and exporter selection, remote W3C parent context is accepted through params._meta, and request or tool content is not captured by default. Stdio servers must use a stderr or remote exporter because stdout is reserved for MCP messages; with no exporter configured, tracing is an effective no-op.