MCP and tool properties support for array of strings and filter conditions

[miguel-xmos]

Hi there, I have an MCP server which I'm trying to connect to which returns the following tools.

{
    "name": "search_docs",
    "description": "Search documentation for a given list of queries....",
    "inputSchema": {
        "$defs": {
            "FieldCondition": {
                "properties": {
                    "key": {
                        "enum": [
                            "page_content",
                            "repo"
                        ],
                        "title": "Key",
                        "type": "string"
                    },
                    "match": {
                        "anyOf": [
                            {
                                "$ref": "#/$defs/MatchValue"
                            },
                            {
                                "$ref": "#/$defs/MatchText"
                            },
                            {
                                "type": "null"
                            }
                        ],
                        "default": null,
                        "title": "Match"
                    }
                },
                "required": [
                    "key"
                ],
                "title": "FieldCondition",
                "type": "object"
            },
            "Filter": {
                "properties": {
                    "should": {
                        "anyOf": [
                            {
                                "items": {
                                    "anyOf": [
                                        {
                                            "$ref": "#/$defs/FieldCondition"
                                        },
                                        {
                                            "$ref": "#/$defs/Filter"
                                        }
                                    ]
                                },
                                "type": "array"
                            },
                            {
                                "type": "null"
                            }
                        ],
                        "default": null,
                        "description": "At least one of those conditions should match",
                        "title": "Should"
                    },
                    "must": {
                        "anyOf": [
                            {
                                "items": {
                                    "anyOf": [
                                        {
                                            "$ref": "#/$defs/FieldCondition"
                                        },
                                        {
                                            "$ref": "#/$defs/Filter"
                                        }
                                    ]
                                },
                                "type": "array"
                            },
                            {
                                "type": "null"
                            }
                        ],
                        "default": null,
                        "description": "All conditions must match",
                        "title": "Must"
                    },
                    "must_not": {
                        "anyOf": [
                            {
                                "items": {
                                    "anyOf": [
                                        {
                                            "$ref": "#/$defs/FieldCondition"
                                        },
                                        {
                                            "$ref": "#/$defs/Filter"
                                        }
                                    ]
                                },
                                "type": "array"
                            },
                            {
                                "type": "null"
                            }
                        ],
                        "default": null,
                        "description": "All conditions must NOT match",
                        "title": "Must Not"
                    }
                },
                "title": "Filter",
                "type": "object"
            },
            "MatchText": {
                "additionalProperties": false,
                "properties": {
                    "text": {
                        "description": "Full-text match of the strings.",
                        "title": "Text",
                        "type": "string"
                    }
                },
                "required": [
                    "text"
                ],
                "title": "MatchText",
                "type": "object"
            },
            "MatchValue": {
                "additionalProperties": false,
                "properties": {
                    "value": {
                        "description": "Exact match of the given value",
                        "title": "Value",
                        "type": "string"
                    }
                },
                "required": [
                    "value"
                ],
                "title": "MatchValue",
                "type": "object"
            }
        },
        "properties": {
            "queries": {
                "items": {
                    "type": "string"
                },
                "title": "Queries",
                "type": "array"
            },
            "content_type": {
                "default": "docs",
                "enum": [
                    "docs",
                    "code"
                ],
                "title": "Content Type",
                "type": "string"
            },
            "condition": {
                "anyOf": [
                    {
                        "$ref": "#/$defs/Filter"
                    },
                    {
                        "type": "null"
                    }
                ],
                "default": null
            },
            "num_docs": {
                "default": 5,
                "title": "Num Docs",
                "type": "integer"
            },
            "offset": {
                "default": 0,
                "title": "Offset",
                "type": "integer"
            }
        },
        "required": [
            "queries"
        ],
        "title": "search_arguments",
        "type": "object"
    }
}

So the issue with this is that

1. the "queries" inputSchema property has a type of "array" which isn't supported isn't supported by Neuron.ai

"queries": {
	"items": {
		"type": "string"
	},
	"title": "Queries",
	"type": "array"
},

2. there's a property called "condition" which doesn't have any type, but contains a reference to a property defined elsewhere in the inputSchema response, again which isn't supported

"condition": {
	"anyOf": [
		{
			"$ref": "#/$defs/Filter"
		},
		{
			"type": "null"
		}
	],
	"default": null
},

Ignoring the fact that none of them have descriptions for the time being. That's an issue also, but can easily be resolved by defaulting the description to an empty string.

Is there any chance we can add support to handle these currently unsupported MCP server responses?

[ilvalerione]

The property type in Neuron is just a string: https://github.com/inspector-apm/neuron-ai/blob/main/src/Tools/ToolProperty.php#L9

It shouldn't matter if you put "array" or "string" or anything else. What error are you getting?

[miguel-xmos]

Yeah, I thought so too when I saw that ToolProperty.php class, however in practice when I tried to pass an array I get the following error

Got error 'PHP message: PHP Fatal error: Uncaught GuzzleHttp\Exception\ClientException: Client error: POST https://api.openai.com/v1/chat/completions resulted in a 400 Bad Request response:\n{\n "error": {\n "message": "Invalid schema for function 'search_docs': In context=('properties', 'queries'), arr (truncated...)\n in /.../vendor/guzzlehttp/guzzle/src/Exception/RequestException.php:111

So when using the following tool definition

Tool::make(
	'search_docs',
	'Search my documentation.'
)->addProperty(
	new ToolProperty(
		name: 'queries',
		type: 'array',
		description: 'List of search query strings.',
		required: false
	)
)->setCallable(function(
	array $queries = []
) {
	if(empty($queries)) return '';	
	//get documentation and return $output
	$output = ['This is just an example'];
	return json_encode($output, JSON_UNESCAPED_UNICODE);
})

I get that error I mentioned, but when I change the 'queries' property from array to string as such

Tool::make(
	'search_docs',
	'Search my documentation.'
)->addProperty(
	new ToolProperty(
		name: 'queries',
		type: 'string',
		description: 'List of search query strings.',
		required: false
	)
)->setCallable(function(
	string $queries = ''
) {
	if(!$queries) return '';
	//get documentation and return $output
	$output = ['This is just an example'];
	return json_encode($output, JSON_UNESCAPED_UNICODE);
})

Then the tool call works successfully.
So while the ToolProperty class accepts arrays, I think perhaps it's not sending that to the AI provider correctly, to OpenAI at least, don't know if other providers work correctly.

[ilvalerione]

@miguel-xmos I just want to inform about important changes in the tool properties definition:

https://docs.neuron-ai.dev/tools-and-function-calls#define-properties