modelcontextprotocol
fix: Restore JSONForm array when all items are simple items
Motivation and Context
Partially resolves of #332 - this PR restores the array logic that was removed in #284, but only when all nested objects are also "simple" objects.
How Has This Been Tested?
Validated against the JSON schema in this comment - nested items are rendered appropriately
Breaking Changes
Types of changes
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [ ] Documentation update
Checklist
- [ ] I have read the MCP Documentation
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
Additional context
Hi @max-stytch I tried testing with a schema based on the shape you linked to but when I click the Add Item button, it doesn't show a field like it does in your screenshot. Have I got the schema wrong?
https://github.com/user-attachments/assets/986f465f-c40c-4c5e-a375-f9edfd85d6d9
Hi @max-stytch we merged a larger set of changes here which I think will have addressed both this and the required issue that you pointed out: https://github.com/modelcontextprotocol/inspector/pull/480
Amazing!
On Fri, Jun 27, 2025 at 9:09 PM Ola Hungerford @.***> wrote:
olaservo left a comment (modelcontextprotocol/inspector#434) https://github.com/modelcontextprotocol/inspector/pull/434#issuecomment-3014926777
Hi @max-stytch https://github.com/max-stytch we merged a larger set of changes here which I think will have addressed both this and the required issue that you pointed out: #480 https://github.com/modelcontextprotocol/inspector/pull/480
— Reply to this email directly, view it on GitHub https://github.com/modelcontextprotocol/inspector/pull/434#issuecomment-3014926777, or unsubscribe https://github.com/notifications/unsubscribe-auth/AVOFOTYI3PQRH5FISY2MZO33FYIRDAVCNFSM6AAAAAB526K32CVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTAMJUHEZDMNZXG4 . You are receiving this because you were mentioned.Message ID: @.***>
@max-stytch I think there were some crossed wires here. @olaservo's comment that led you to close this I think was mistaken. This was about the form handling and #480 was about fixing a problem where we had the required field as a boolean rather than an array. I think we still need this. We also need a tool in the everything server that has a complex inputSchema to test with.
I was doing unrelated inputSchema investigation with a testing server and tool, and had taken note of this issue, so I checked the form rendering. I think the form for arrays is fixed.
There is a slight quirk, that objects with typed properties do not initialize default values the same as primitive fields. Skimming the code, I think this is because in the object case getArrayItemDefault() is not called for the default values of the types of the object properties. Also, the typed_objects object case might be sorted out by inspecting additionalProperties, not properties. All of this is in isSimpleObject().
Here's the tool schema, and a screenshot of the form. (I added alternating bounding boxes in the screenshot just to make the form layout clearer. I think the layout can be improved.)
I can add such a tool to the Everything Server.
{
"tools": [
{
"name": "complex_input_schema_tool",
"description": "Tool that handles complex input schemas with mixed-type arrays.",
"inputSchema": {
"type": "object",
"properties": {
"numbers": {
"description": "An array of numbers",
"items": {
"type": "number"
},
"title": "Numbers",
"type": "array"
},
"strings": {
"description": "An array of strings",
"items": {
"type": "string"
},
"title": "Strings",
"type": "array"
},
"objects": {
"description": "An array of objects (dicts)",
"items": {
"additionalProperties": true,
"type": "object"
},
"title": "Objects",
"type": "array"
},
"typed_objects": {
"description": "An array of objects with 'word' (str) and 'length' (int) properties",
"items": {
"additionalProperties": {
"anyOf": [
{
"type": "string"
},
{
"type": "integer"
}
]
},
"type": "object"
},
"title": "Typed Objects",
"type": "array"
},
"structured_objects": {
"description": "An array of structured objects with defined word and length properties",
"items": {
"properties": {
"word": {
"title": "Word",
"type": "string"
},
"length": {
"title": "Length",
"type": "integer"
}
},
"required": [
"word",
"length"
],
"title": "WordItem",
"type": "object"
},
"title": "Structured Objects",
"type": "array"
},
"mixed": {
"description": "An array of non-uniform types (int, str, bool, dict, etc.)",
"items": {},
"title": "Mixed",
"type": "array"
},
"str_and_int": {
"description": "An array containing only strings and integers",
"items": {
"anyOf": [
{
"type": "string"
},
{
"type": "integer"
}
]
},
"title": "Str And Int",
"type": "array"
}
},
"required": [
"numbers",
"strings",
"objects",
"typed_objects",
"structured_objects",
"mixed",
"str_and_int"
]
},
"outputSchema": {
"type": "object",
"properties": {
"result": {
"title": "Result",
"type": "string"
}
},
"required": [
"result"
],
},
"_meta": {
"_fastmcp": {
"tags": []
}
}
}
]
}
I was doing unrelated
inputSchemainvestigation with a testing server and tool, and had taken note of this issue, so I checked the form rendering. I think the form for arrays is fixed
@richardkmichael Fixed in the existing Inspector or with this PR?
I can add such a tool to the Everything Server.
This would be nice.
I was doing unrelated
inputSchemainvestigation with a testing server and tool, and had taken note of this issue, so I checked the form rendering. I think the form for arrays is fixed@richardkmichael Fixed in the existing Inspector or with this PR?
On main, without this PR. (Sorry, I had realized my comment was ambiguous and meant to come back and edit it.)
I can add such a tool to the Everything Server.
This would be nice.
Will do.