fix: add list type support for ToolInput constant value in tool node

[qiaofenlin]

• Add list type validation for checkbox multi-select parameters
• Align ToolInput validation with TriggerEventInput behavior
• Fix ValidationError when using checkbox type tool parameters

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Fixes #31282

Summary

This PR fixes a validation error when using checkbox (multi-select) type parameters in tool nodes.

Problem

When a tool node has a checkbox parameter, executing the workflow fails with:

ValidationError: 1 validation error for ToolInput type Value error, value must be a string, int, float, bool or dict

Root Cause

Checkbox multi-select controls store values as arrays (e.g., ['female']), but the ToolInput validator in tool nodes did not support list type, while TriggerEventInput in trigger nodes already does.

Comparison:

Node Type	Supported value types
Trigger Node (TriggerEventInput)	str, int, float, bool, dict, list ✅
Tool Node (ToolInput)	str, int, float, bool, dict ❌

Solution

Add list type support to ToolInput.check_type() validator to align with TriggerEventInput behavior.

Changes

• api/core/workflow/nodes/tool/entities.py: Add list type validation for constant value in ToolInput

Screenshots

Before	After
ValidationError when using checkbox parameters in tool node	Tool node executes successfully with checkbox parameters

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint and make type-check (backend) and cd web && npx lint-staged (frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @qiaofenlin, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical validation issue within the workflow system, specifically concerning tool nodes that utilize multi-select checkbox parameters. Previously, these parameters, which inherently produce list-type values, were not correctly validated by the ToolInput mechanism, leading to runtime errors. The change introduces support for list-type constant values in ToolInput, harmonizing its validation logic with that of TriggerEventInput and thereby enabling seamless execution of workflows with such configurations.

Highlights

• Fix Validation Error: Resolves a ValidationError that occurred when using checkbox (multi-select) type parameters in tool nodes, which previously failed due to unsupported list values.
• Align ToolInput Validation: Adds list type support to the ToolInput.check_type() validator, bringing its behavior in line with TriggerEventInput which already supported list types.
• Enhanced Workflow Robustness: Ensures that workflows utilizing multi-select checkbox parameters in tool nodes can execute successfully without encountering type validation issues.

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[gemini-code-assist]

Code Review

This pull request correctly addresses the ValidationError for checkbox multi-select parameters in tool nodes by adding list to the allowed types for ToolInput constants. The change is straightforward and aligns ToolInput with TriggerEventInput as intended. I have one suggestion to improve the maintainability of the type validation logic.