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Merge pull request #311 from koic/remove_server_sampling_direct_call

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Remove `Server#create_sampling_message` direct call
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Koichi ITO 2026-04-15 02:33:26 +09:00 • committed by GitHub
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README.md
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@ -876,8 +876,7 @@ This enables servers to leverage the client's LLM capabilities without needing d
**Using Sampling in Tools:**
Tools that accept a `server_context:` parameter can call `create_sampling_message` on it.
The request is automatically routed to the correct client session.
Set `server.server_context = server` so that `server_context.create_sampling_message` delegates to the server:
The request is automatically routed to the correct client session:
```ruby
class SummarizeTool < MCP::Tool
@ -905,7 +904,6 @@ class SummarizeTool < MCP::Tool
end
server = MCP::Server.new(name: "my_server", tools: [SummarizeTool])
server.server_context = server
```
**Parameters:**
@ -926,86 +924,8 @@ Optional:
- `tools:` (Array) - Tools available to the LLM (requires `sampling.tools` capability)
- `tool_choice:` (Hash) - Tool selection mode (e.g., `{ mode: "auto" }`)
**Direct Usage:**
`Server#create_sampling_message` can also be called directly outside of tools:
```ruby
result = server.create_sampling_message(
messages: [
{ role: "user", content: { type: "text", text: "What is the capital of France?" } }
],
max_tokens: 100,
system_prompt: "You are a helpful assistant.",
temperature: 0.7
)
```
Result contains the LLM response:
```ruby
{
role: "assistant",
content: { type: "text", text: "The capital of France is Paris." },
model: "claude-3-sonnet-20240307",
stopReason: "endTurn"
}
```
For multi-client transports (e.g., `StreamableHTTPTransport`), use `server_context.create_sampling_message` inside tools
to route the request to the correct client session.
**Tool Use in Sampling:**
When tools are provided in a sampling request, the LLM can call them during generation.
The server must handle tool calls and continue the conversation with tool results:
```ruby
result = server.create_sampling_message(
messages: [
{ role: "user", content: { type: "text", text: "What's the weather in Paris?" } }
],
max_tokens: 1000,
tools: [
{
name: "get_weather",
description: "Get weather for a city",
inputSchema: {
type: "object",
properties: { city: { type: "string" } },
required: ["city"]
}
}
],
tool_choice: { mode: "auto" }
)
if result[:stopReason] == "toolUse"
tool_results = result[:content].map do |tool_use|
weather_data = get_weather(tool_use[:input][:city])
{
type: "tool_result",
toolUseId: tool_use[:id],
content: [{ type: "text", text: weather_data.to_json }]
}
end
final_result = server.create_sampling_message(
messages: [
{ role: "user", content: { type: "text", text: "What's the weather in Paris?" } },
{ role: "assistant", content: result[:content] },
{ role: "user", content: tool_results }
],
max_tokens: 1000,
tools: [...]
)
end
```
**Error Handling:**
- Raises `RuntimeError` if transport is not set
- Raises `RuntimeError` if client does not support `sampling` capability
- Raises `RuntimeError` if `tools` are used but client lacks `sampling.tools` capability
- Raises `StandardError` if client returns an error response