4d79997120
The License section named MIT. LICENSE is a transition file: new code contributions are Apache-2.0, documentation excluding specifications is CC-BY-4.0, and only earlier contributions without relicensing consent stay MIT. "Rust (stable)" understates the floor. rmcp, darling and time declare rust-version 1.88, and cargo metadata resolves both crates to 1.88. The Ruby aside said 3.3 also satisfies the gems. anthropic requires >= 3.2.0 and mcp >= 2.7.0, so the gem floor was 3.2, and 3.2 reached EOL on 2026-03-31. CI runs 3.4, which is what the READMEs now state. The Go and Rust clients take a command plus arguments, not a path to a server script. Removed the commit-message convention, which is attributed to the MCP contributing guidelines but does not appear in them. Added the AI_POLICY.md link that CONTRIBUTING.md points to. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GdvHa5MzDw33PEz3DbTaJD
41 lines
2 KiB
Markdown
41 lines
2 KiB
Markdown
# An LLM-Powered Chatbot MCP Client written in Ruby
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An interactive chatbot MCP client: it launches an MCP server over stdio, lists its tools, and hands them to Claude, which can call them while answering your questions.
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This example accompanies the [Build an MCP client](https://modelcontextprotocol.io/docs/develop/build-client) tutorial.
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## Prerequisites
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- Ruby 3.4+
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- Bundler
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- An [Anthropic API key](https://console.anthropic.com/) (optional — see below)
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## Setup
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Install the gems, then put your API key in a `.env` file (or export `ANTHROPIC_API_KEY` in your shell):
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```bash
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bundle install
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cp .env.example .env
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# then edit .env and add your key
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```
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## Run the client
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Pass the path to a server script. `.rb` servers are launched with `ruby`, `.py` with `python3`, and `.js` with `node`:
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```bash
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bundle exec ruby client.rb ../weather-server-ruby/weather.rb
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```
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Type a question (for example, "What's the weather in Sacramento?") and Claude answers using the server's tools. Type `quit` to exit.
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Without an `ANTHROPIC_API_KEY`, the client still connects, prints the server's tools, and exits — useful for verifying the MCP wiring without credentials.
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## Structured content
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The spec says clients SHOULD validate structured results against the schema the tool declares, and this SDK's client does not do it for you — `MCP::Client::Tool#output_schema` hands back the raw schema from the wire and nothing checks results against it. So the client compiles each declared schema once at connect time with `MCP::Tool::OutputSchema.new` and validates every non-error result.
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The two channels go to different readers: `content` is forwarded to the model, while `structured_content` is used as data — when a tool returns an array, the client counts its items rather than re-reading the prose. See [Structured Content](https://modelcontextprotocol.io/specification/2026-07-28/server/tools#structured-content).
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`MCP::Client::Stdio` offers `2026-07-28` by default, so no negotiation setup is needed here.
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