Missing title and arguments fields in Prompt definition (spec compliance)

While working with the Prompt API, I noticed a discrepancy between the official MCP specification and the current PHP SDK implementation.

According to the Model Context Protocol Specification:

The prompt object supports the following optional fields:

title: Optional human-readable name of the prompt for display purposes

arguments: Optional list of arguments for prompt customization

However, these fields do not appear to be supported or exposed in the current PHP SDK.

Expected behavior

The PHP SDK should support:

Defining a title for prompts
Defining and passing arguments for prompt parameterization

Current behavior

There is no way to:

Set a human-readable title for a prompt
Define structured arguments for prompt customization

Why this matters

title improves usability in UIs and tooling
arguments are essential for building reusable and parameterized prompts
Lack of support leads to incomplete spec compliance and limits interoperability

Suggested solution

Extend the Prompt definition in the SDK to include:
- title?: string
- arguments?: array
Ensure serialization/deserialization aligns with the MCP spec
Optionally provide helper classes or typing for arguments

Add `title` field to Prompt for MCP spec compliance

@vjik

Thanks for reporting @vjik - I patched the missing title with #278 - to be released with upcomgin v0.5.0.

Regarding the arguments I'm afraid that's a mixup, they are already in:

php-sdk/src/Schema/Prompt.php

Line 44 in 863cfc1

Even with a subtype PromptArgument:

php-sdk/src/Schema/PromptArgument.php

Lines 27 to 39 in 863cfc1

    
           class PromptArgument implements \JsonSerializable 
        
           { 
        
               /** 
        
                * @param string      $name        the name of the argument 
        
                * @param string|null $description a human-readable description of the argument 
        
                * @param bool|null   $required    Whether this argument must be provided. Defaults to false per MCP spec if omitted. 
        
                */ 
        
               public function __construct( 
        
                   public readonly string $name, 
        
                   public readonly ?string $description = null, 
        
                   public readonly ?bool $required = null, 
        
               ) { 
        
               }

Regarding the arguments I'm afraid that's a mixup, they are already in:

You're right, there is arguments in schema. title and arguments are missed in Builder::addPrompt() method:

php-sdk/src/Server/Builder.php

Line 461 in 1f5f7e1

public function addPrompt(

That is true, and due to the fact that arguments are discovered from the parameter profile of the implementation of a prompt, see

php-sdk/src/Capability/Registry/Loader/ArrayLoader.php

Lines 234 to 252 in 863cfc1

    
           $arguments = []; 
        
           $paramTags = $reflection instanceof \ReflectionMethod ? $docBlockParser->getParamTags( 
        
               $docBlockParser->parseDocBlock($reflection->getDocComment() ?? null), 
        
           ) : []; 
        
           foreach ($reflection->getParameters() as $param) { 
        
               $reflectionType = $param->getType(); 
        
               // Basic DI check (heuristic) 
        
               if ($reflectionType instanceof \ReflectionNamedType && !$reflectionType->isBuiltin()) { 
        
                   continue; 
        
               } 
        
               $paramTag = $paramTags['$'.$param->getName()] ?? null; 
        
               $arguments[] = new PromptArgument( 
        
                   $param->getName(), 
        
                   $paramTag ? trim((string) $paramTag->getDescription()) : null, 
        
                   !$param->isOptional() && !$param->isDefaultValueAvailable(), 
        
               ); 
        
           }

Can you maybe share a bit more how your prompt implementation looks like and what your expectations would be?

Add `title` field to Prompt for MCP spec compliance

That is true, and due to the fact that arguments are discovered from the parameter profile of the implementation of a prompt

I want to set prompt arguments clearly. Seems, in this case I should implement own loader.

Add `title` field to Prompt for MCP spec compliance (modelcontextprot…

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Missing `title` and `arguments` fields in Prompt definition (spec compliance) #276

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	class PromptArgument implements \JsonSerializable
	{
	/**
	* @param string $name the name of the argument
	* @param string\|null $description a human-readable description of the argument
	* @param bool\|null $required Whether this argument must be provided. Defaults to false per MCP spec if omitted.
	*/
	public function __construct(
	public readonly string $name,
	public readonly ?string $description = null,
	public readonly ?bool $required = null,
	) {
	}

	$arguments = [];
	$paramTags = $reflection instanceof \ReflectionMethod ? $docBlockParser->getParamTags(
	$docBlockParser->parseDocBlock($reflection->getDocComment() ?? null),
	) : [];
	foreach ($reflection->getParameters() as $param) {
	$reflectionType = $param->getType();

	// Basic DI check (heuristic)
	if ($reflectionType instanceof \ReflectionNamedType && !$reflectionType->isBuiltin()) {
	continue;
	}

	$paramTag = $paramTags['$'.$param->getName()] ?? null;
	$arguments[] = new PromptArgument(
	$param->getName(),
	$paramTag ? trim((string) $paramTag->getDescription()) : null,
	!$param->isOptional() && !$param->isDefaultValueAvailable(),
	);
	}

Sunbelt Computer Software

PL/B Language Development and Support

Missing title and arguments fields in Prompt definition (spec compliance) #276

Description

Expected behavior

Current behavior

Why this matters

Suggested solution

Activity

chr-hertel commented on Apr 11, 2026

vjik commented on Apr 12, 2026

chr-hertel commented on Apr 13, 2026

vjik commented on Apr 14, 2026

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Missing `title` and `arguments` fields in Prompt definition (spec compliance) #276