ValidateTools

Overview

The ValidateTools block validates that AI models call the correct tools/functions with the right arguments. Essential for testing AI agents and function-calling models.

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "expected": ["search_database", "send_email"]
  },
  "output": "toolValidation"
}

Input Parameters

Required

Parameter	Type	Description
`toolCalls`	array	Array of tool call objects

Each tool call object should have:

{
  name: "tool_name",      // or toolName
  args: { /* ... */ }     // optional arguments
}

Configuration

All config parameters are optional:

Parameter	Type	Description
`expected`	string/array	Required tool names
`forbidden`	string/array	Tools that should NOT be called
`minTools`	number	Minimum number of tools that should be called
`maxTools`	number	Maximum number of tools allowed
`order`	array	Expected order of tool calls
`validateArgs`	object	Expected arguments for each tool

Output Fields

Field	Type	Description
`passed`	boolean	Whether all validations passed
`failures`	array	List of validation failures
`score`	number	Validation score (0.0 - 1.0)
`actualTools`	array	Tool names that were actually called
`expectedTools`	array	Tool names that were expected

Examples

Validate Expected Tools

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "expected": ["search_database", "send_email"]
  },
  "output": "validation"
}

Success:

{
  passed: true,
  failures: [],
  score: 1.0,
  actualTools: ["search_database", "send_email"],
  expectedTools: ["search_database", "send_email"]
}

Failure:

{
  passed: false,
  failures: ["Missing expected tools: send_email"],
  score: 0.5,
  actualTools: ["search_database"],
  expectedTools: ["search_database", "send_email"]
}

Forbid Dangerous Tools

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "forbidden": ["delete_database", "drop_table"]
  },
  "output": "validation"
}

Validate Tool Count

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "minTools": 1,
    "maxTools": 3
  },
  "output": "validation"
}

Validate Tool Order

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "order": ["get_user", "update_profile", "send_notification"]
  },
  "output": "validation"
}

Validate Tool Arguments

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "expected": ["search_database"],
    "validateArgs": {
      "search_database": {
        "table": "users",
        "limit": 10
      }
    }
  },
  "output": "validation"
}

Combined Validations

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "expected": ["search_users", "send_email"],
    "forbidden": ["delete_user"],
    "minTools": 2,
    "maxTools": 3,
    "validateArgs": {
      "search_users": {
        "limit": 10
      }
    }
  },
  "output": "validation"
}

Common Patterns

Test AI Agent Tool Usage

{
  "name": "AI Agent Tool Test",
  "tests": [{
    "id": "test-calendar-agent",
    "pipeline": [
      {
        "block": "HttpRequest",
        "input": {
          "url": "${AI_API_URL}/chat",
          "method": "POST",
          "body": {
            "messages": [{
              "role": "user",
              "content": "Schedule a meeting for tomorrow at 2pm"
            }],
            "tools": [
              { "name": "search_calendar" },
              { "name": "create_event" }
            ]
          }
        },
        "output": "response"
      },
      {
        "block": "StreamParser",
        "input": "${response.body}",
        "config": { "format": "sse-openai" },
        "output": {
          "toolCalls": "toolCalls"
        }
      },
      {
        "block": "ValidateTools",
        "input": {
          "from": "toolCalls",
          "as": "toolCalls"
        },
        "config": {
          "expected": ["search_calendar", "create_event"],
          "order": ["search_calendar", "create_event"]
        },
        "output": "toolValidation"
      }
    ],
    "assertions": {
      "toolValidation.passed": true
    }
  }]
}

Ensure Safe Tool Usage

{
  "pipeline": [
    {
      "block": "HttpRequest",
      "input": {
        "url": "${AI_URL}/chat",
        "method": "POST",
        "body": {
          "message": "Delete my account"
        }
      },
      "output": "response"
    },
    {
      "block": "StreamParser",
      "input": "${response.body}",
      "output": { "toolCalls": "tools" }
    },
    {
      "block": "ValidateTools",
      "input": {
        "from": "tools",
        "as": "toolCalls"
      },
      "config": {
        "forbidden": ["delete_account", "drop_database"]
      },
      "output": "safety"
    }
  ],
  "assertions": {
    "safety.passed": true
  }
}

Validate Multi-Step Agent

{
  "block": "ValidateTools",
  "input": {
    "from": "aiResponse.toolCalls",
    "as": "toolCalls"
  },
  "config": {
    "order": [
      "authenticate_user",
      "fetch_data",
      "process_data",
      "send_response"
    ]
  },
  "output": "validation"
}

Tool Call Format

The block expects tool calls in this format:

[
  {
    name: "search_database",  // or toolName
    args: {
      query: "users",
      limit: 10
    }
  },
  {
    name: "send_email",
    args: {
      to: "user@example.com",
      subject: "Hello"
    }
  }
]

Compatible with:

OpenAI function calling format
Anthropic tool use format
Vercel AI SDK tool calls

StreamParser automatically extracts tool calls into this format from streaming responses.

Validation Score

The score field represents validation quality:

1.0 - All validations passed
0.5 - 0.9 - Some issues (missing tools, wrong order)
< 0.5 - Significant issues (forbidden tools used, major mismatches)

Factors that reduce score:

Missing expected tools
Using forbidden tools
Wrong tool count
Incorrect order
Argument mismatches

Error Messages

Common failure messages:

Message	Cause
`Missing expected tools: tool1, tool2`	Expected tools not called
`Used forbidden tools: tool1`	Forbidden tool was called
`Too few tools: 1 < 2`	Below minTools
`Too many tools: 5 > 3`	Above maxTools
`Tool order incorrect`	Tools called in wrong order
`Tool 'search' arg 'limit' mismatch`	Tool argument doesn’t match expected value

Full Example

{
  "name": "Customer Service Agent Test",
  "context": {
    "AI_URL": "${env.AI_API_URL}",
    "API_KEY": "${env.API_KEY}"
  },
  "tests": [{
    "id": "test-customer-query",
    "pipeline": [
      {
        "id": "call-agent",
        "block": "HttpRequest",
        "input": {
          "url": "${AI_URL}/chat",
          "method": "POST",
          "headers": {
            "Authorization": "Bearer ${API_KEY}"
          },
          "body": {
            "messages": [{
              "role": "user",
              "content": "Look up my order #12345 and send me an update"
            }],
            "tools": [
              { "name": "search_orders", "description": "Search orders" },
              { "name": "send_email", "description": "Send email" }
            ]
          }
        },
        "output": "response"
      },
      {
        "id": "parse-stream",
        "block": "StreamParser",
        "input": "${response.body}",
        "config": {
          "format": "sse-openai"
        },
        "output": {
          "text": "aiMessage",
          "toolCalls": "toolCalls"
        }
      },
      {
        "id": "validate-tools",
        "block": "ValidateTools",
        "input": {
          "from": "toolCalls",
          "as": "toolCalls"
        },
        "config": {
          "expected": ["search_orders", "send_email"],
          "order": ["search_orders", "send_email"],
          "minTools": 2,
          "maxTools": 2,
          "validateArgs": {
            "search_orders": {
              "order_id": "12345"
            }
          }
        },
        "output": "toolValidation"
      }
    ],
    "assertions": {
      "response.status": 200,
      "toolValidation.passed": true,
      "toolValidation.score": { "gt": 0.9 }
    }
  }]
}

Tips

Use StreamParser First

StreamParser extracts tool calls from streaming responses:

{
  "pipeline": [
    {
      "block": "HttpRequest",
      "output": "response"
    },
    {
      "block": "StreamParser",
      "input": "${response.body}",
      "output": { "toolCalls": "tools" }
    },
    {
      "block": "ValidateTools",
      "input": { "from": "tools", "as": "toolCalls" },
      "config": { "expected": ["search"] },
      "output": "validation"
    }
  ]
}

Order Matters for Multi-Step Agents

Use order to validate sequential tool usage:

{
  "config": {
    "order": ["auth", "fetch", "process", "respond"]
  }
}

Combine with LLMJudge

ValidateTools checks structure, LLMJudge checks reasoning:

{
  "pipeline": [
    {
      "block": "ValidateTools",
      "config": { "expected": ["search"] },
      "output": "toolCheck"
    },
    {
      "block": "LLMJudge",
      "input": {
        "text": "${aiMessage}",
        "expected": {
          "expectedBehavior": "Polite customer service"
        }
      },
      "output": "qualityCheck"
    }
  ],
  "assertions": {
    "toolCheck.passed": true,
    "qualityCheck.score": { "gt": 0.7 }
  }
}

Use Forbidden for Safety

Prevent dangerous operations:

{
  "config": {
    "forbidden": [
      "delete_user",
      "drop_table",
      "execute_sql",
      "send_money"
    ]
  }
}

When to Use

Use ValidateTools when:

Testing AI function calling
Validating agent tool usage
Ensuring safe tool execution
Testing multi-step workflows
Verifying tool arguments

Don’t use when:

No tool/function calling involved
Testing pure text generation
Validating non-AI responses

Next Steps

StreamParser

Parse streaming responses with tool calls

LLMJudge

Validate AI response quality

Get Started

Core Concepts

Blocks

Testing AI Systems

Advanced

Overview

Input Parameters

Required

Configuration

Output Fields

Examples

Validate Expected Tools

Forbid Dangerous Tools

Validate Tool Count

Validate Tool Order

Validate Tool Arguments

Combined Validations

Common Patterns

Test AI Agent Tool Usage

Ensure Safe Tool Usage

Validate Multi-Step Agent

Tool Call Format

Validation Score

Error Messages

Full Example

Tips

When to Use

Next Steps

StreamParser

LLMJudge

Get Started

Core Concepts

Blocks

Testing AI Systems

Advanced

​Overview

​Input Parameters

​Required

​Configuration

​Output Fields

​Examples

​Validate Expected Tools

​Forbid Dangerous Tools

​Validate Tool Count

​Validate Tool Order

​Validate Tool Arguments

​Combined Validations

​Common Patterns

​Test AI Agent Tool Usage

​Ensure Safe Tool Usage

​Validate Multi-Step Agent

​Tool Call Format

​Validation Score

​Error Messages

​Full Example

​Tips

​When to Use

​Next Steps

StreamParser

LLMJudge

Overview

Input Parameters

Required

Configuration

Output Fields

Examples

Validate Expected Tools

Forbid Dangerous Tools

Validate Tool Count

Validate Tool Order

Validate Tool Arguments

Combined Validations

Common Patterns

Test AI Agent Tool Usage

Ensure Safe Tool Usage

Validate Multi-Step Agent

Tool Call Format

Validation Score

Error Messages

Full Example

Tips

When to Use

Next Steps