82aac972c1* feat: support sampling with tools * address sampling tools review feedback * tighten sampling tools spec compliance * drop SamplingStopReason enum in favor of open string The spec leaves stopReason open for provider-specific values, so upcasting the four known ones to enum cases makes every future enum addition a silent BC break for string comparisons. --------- Co-authored-by: Christopher Hertel <mail@christopher-hertel.de>
82 lines
2.9 KiB
Markdown
82 lines
2.9 KiB
Markdown
# Client Communication
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MCP supports various ways a server can communicate back to a server on top of the main request-response flow.
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## Table of Contents
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- [ClientGateway](#client-gateway)
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- [Sampling](#sampling)
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- [Logging](#logging)
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- [Notification](#notification)
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- [Progress](#progress)
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## ClientGateway
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Every communication back to client is handled using the `Mcp\Server\ClientGateway` and its dedicated methods per
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operation. To use the `ClientGateway` in your code, you need to use method argument injection for `RequestContext`.
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Every reference of a MCP element, that translates to an actual method call, can just add an type-hinted argument for the
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`RequestContext` and the SDK will take care to include the gateway in the arguments of the method call:
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```php
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use Mcp\Capability\Attribute\McpTool;
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use Mcp\Server\RequestContext;
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class MyService
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{
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#[McpTool(name: 'my_tool', description: 'My Tool Description')]
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public function myTool(RequestContext $context): string
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{
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$context->getClientGateway()->log(...);
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```
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## Sampling
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With [sampling](https://modelcontextprotocol.io/specification/2025-11-25/client/sampling) servers can request clients to
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execute "completions" or "generations" with a language model for them:
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```php
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$result = $clientGateway->sample('Roses are red, violets are', 350, 90, ['temperature' => 0.5]);
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```
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The `sample` method accepts four arguments:
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1. `message`, which is **required** and accepts a string, an instance of `Content` or an array of `SamplingMessage` instances.
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2. `maxTokens`, which defaults to `1000`
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3. `timeout` in seconds, which defaults to `120`
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4. `options` which might include `systemPrompt`, `preferences` for model choice, `includeContext`, `temperature`,
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`stopSequences`, `metadata`, `tools`, and `toolChoice`
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Only send `includeContext` when the client advertises `sampling.context`, and only send `tools` or `toolChoice` when it
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advertises `sampling.tools`. The context modes other than `none` are soft-deprecated by the current specification.
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[Find more details to sampling payload in the specification.](https://modelcontextprotocol.io/specification/2025-11-25/client/sampling#protocol-messages)
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## Logging
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The [Logging](https://modelcontextprotocol.io/specification/2025-06-18/server/utilities/logging) utility enables servers
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to send structured log messages as notification to clients:
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```php
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use Mcp\Schema\Enum\LoggingLevel;
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$clientGateway->log(LoggingLevel::Warning, 'The end is near.');
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```
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## Progress
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With a [Progress](https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/progress#progress)
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notification a server can update a client while an operation is ongoing:
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```php
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$clientGateway->progress(4.2, 10, 'Downloading needed images.');
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```
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## Notification
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Lastly, the server can push all kind of notifications, that implement the `Mcp\Schema\JsonRpc\Notification` interface
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to the client to:
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```php
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$clientGateway->notify($yourNotification);
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```
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