d59950f1acRequestMeta::parseTraceContext() now falls back to the native traceparent/ tracestate/baggage HTTP headers when _meta carries none, and HeaderFactory mirrors an application-set _meta trace context onto those same headers on outbound requests. _meta wins when both are present.
102 lines
3.5 KiB
PHP
102 lines
3.5 KiB
PHP
<?php
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/*
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* This file is part of the official PHP MCP SDK.
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*
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* A collaboration between Symfony and the PHP Foundation.
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Mcp\Client\Stateless;
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use Mcp\Schema\Enum\ProtocolVersion;
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use Mcp\Schema\Wire\McpHeader;
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use Mcp\Server\Stateless\RequestMeta;
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/**
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* The HTTP headers a modern-era client puts on every POST (SEP-2243, SEP-2575).
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*
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* These exist so an intermediary can route and authorize MCP traffic without
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* parsing the body. That only works if the headers cannot disagree with what
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* they mirror, so they are derived here from the very message that is about to
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* be sent — never from what the caller believes it is sending.
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*
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* @see \Mcp\Server\Stateless\StandardHeaderValidator the server that checks this
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*
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* @author Christopher Hertel <mail@christopher-hertel.de>
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*/
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final class HeaderFactory
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{
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public function __construct(
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private readonly ToolCatalog $tools,
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) {
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}
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/**
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* @param array<string, mixed> $payload a serialized JSON-RPC message
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*
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* @return array<string, string>
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*/
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public function forMessage(array $payload, ProtocolVersion $protocolVersion): array
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{
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$method = $payload['method'] ?? null;
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$params = \is_array($payload['params'] ?? null) ? $payload['params'] : null;
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// A response to a server-initiated request carries no method to mirror;
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// the version header is unconditional and still applies. Trace context
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// still rides along if the application put it in `_meta` — the party
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// that started the trace is not necessarily the one with a method to
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// report.
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if (!\is_string($method)) {
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return [McpHeader::PROTOCOL_VERSION => $protocolVersion->value, ...$this->traceHeaders($params)];
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}
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$headers = [
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McpHeader::PROTOCOL_VERSION => $protocolVersion->value,
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McpHeader::METHOD => $method,
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...$this->traceHeaders($params),
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];
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if (null !== $name = McpHeader::nameFor($method, $params)) {
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// Tool and prompt names are only SHOULD-constrained to header-safe
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// characters and a resource URI is not constrained at all, so
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// anything unsafe is wrapped rather than dropped or mangled.
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$headers[McpHeader::NAME] = McpHeader::encode($name) ?? $name;
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}
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if ('tools/call' === $method && \is_string($params['name'] ?? null)) {
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$arguments = \is_array($params['arguments'] ?? null) ? $params['arguments'] : [];
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foreach ($this->tools->headersFor($params['name'], $arguments) as $suffix => $value) {
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$headers[McpHeader::PARAM_PREFIX.$suffix] = $value;
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}
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}
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return $headers;
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}
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/**
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* Mirrors W3C trace context from `_meta` onto its native HTTP headers, so
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* an application that only knows how to set `_meta` — the transport-agnostic
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* surface — still gets header-based propagation for free on HTTP.
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*
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* @param array<string, mixed>|null $params
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*
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* @return array<string, string>
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*/
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private function traceHeaders(?array $params): array
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{
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$meta = \is_array($params['_meta'] ?? null) ? $params['_meta'] : [];
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$headers = [];
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foreach (RequestMeta::TRACE_KEYS as $key) {
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if (\is_string($meta[$key] ?? null)) {
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$headers[$key] = $meta[$key];
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}
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}
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return $headers;
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}
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}
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