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Remove Server#create_sampling_message direct call #311

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82 changes: 1 addition & 81 deletions README.md
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -823,8 +823,7 @@ 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
Expand Down Expand Up @@ -852,7 +851,6 @@ class SummarizeTool < MCP::Tool
end

server = MCP::Server.new(name: "my_server", tools: [SummarizeTool])
server.server_context = server
```

**Parameters:**
Expand All @@ -873,86 +871,8 @@ 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
Expand Down
38 changes: 0 additions & 38 deletions lib/mcp/server.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -206,44 +206,6 @@ def notify_log_message(data:, level:, logger: nil)
report_exception(e, { notification: "log_message" })
end

# Sends a `sampling/createMessage` request to the client.
# For single-client transports (e.g., `StdioTransport`). For multi-client transports
# (e.g., `StreamableHTTPTransport`), use `ServerSession#create_sampling_message` instead
# to ensure the request is routed to the correct client.
def create_sampling_message(
messages:,
max_tokens:,
system_prompt: nil,
model_preferences: nil,
include_context: nil,
temperature: nil,
stop_sequences: nil,
metadata: nil,
tools: nil,
tool_choice: nil,
related_request_id: nil
)
unless @transport
raise "Cannot send sampling request without a transport."
end

params = build_sampling_params(
@client_capabilities,
messages: messages,
max_tokens: max_tokens,
system_prompt: system_prompt,
model_preferences: model_preferences,
include_context: include_context,
temperature: temperature,
stop_sequences: stop_sequences,
metadata: metadata,
tools: tools,
tool_choice: tool_choice,
)

@transport.send_request(Methods::SAMPLING_CREATE_MESSAGE, params)
end

# Sets a custom handler for `resources/read` requests.
# The block receives the parsed request params and should return resource
# contents. The return value is set as the `contents` field of the response.
Expand Down
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