Build Smarter, Faster: Introducing HubSpot’s Developer Tool Testing Agent

Building AI-powered tools inside HubSpot often requires trial, error, and careful debugging. Developers need a way to validate tool behavior, understand how agents interpret instructions, and test sequential tool execution before deploying anything to customers.

HubSpot’s Developer Tool Testing Agent is designed exactly for that. This flexible, diagnostic agent helps developers simulate real agent behavior, identify problems early, and refine their tool setup with clearer insights than a standard agent provides.

Whether you're building a new tool, customizing an internal workflow, or experimenting with multi-step tool invocation, the Developer Tool Testing Agent gives you a safe environment to test, iterate, and perfect your build.

What Is the Developer Tool Testing Agent?

Unlike other HubSpot agents that perform specific business tasks, the Developer Tool Testing Agent is intentionally open-ended. It’s built to:

• Test custom tools

• Debug tool invocation

• Validate parameter passing

• Examine step-by-step reasoning

• Simulate other agent types (e.g., Brand Voice, Brand Assistant, Content Builder)

• Help developers design structured plans before implementation

Because it is lightly structured, it can mimic other agents simply by adjusting your instructions or adding the appropriate tools.

This makes it invaluable during development, especially when working with tool sequences, chained logic, or complex input/output patterns.

Why Developers Love This Agent

The Developer Tool Testing Agent isn't just another utility—it’s a complete development sandbox for anyone building HubSpot agent tools.

Here are the core benefits:

1. Tool Invocation Testing

You can add your own custom tools to this agent and watch how it:

• Chooses which tool to invoke

• Passes parameters

• Executes tools in sequence

• Handles outputs and errors

This is critical for ensuring your production agents behave correctly.

2. Step-by-Step Reasoning & Diagnostics

Unlike fully polished agents, this one intentionally gives verbose explanations, allowing you to analyze:

• The agent’s internal thought process

• Why it selected certain tools

• Where reasoning breaks down

• Gaps in your instructions or configuration

This insight makes debugging significantly easier.

3. Flexible Simulation

Because the agent comes with minimal built-in tools and loose instructions, you can customize it to behave like:

• A Brand Voice agent

• A Content Creation agent

• A Research agent

• A Data Transformation agent

• Or any agent you're planning to build

This gives developers a realistic environment to test before going live.

4. Sequential Tool Execution

If you’re building multi-step workflows, the Developer Tool Testing Agent helps ensure:

• Step 1 passes correct output to Step 2

• Dependencies are respected

• Tool order makes sense

• The agent chains tasks together without errors

This is crucial for complex operations.

How to Configure the Agent

When you open the Developer Tool Testing Agent, you’ll see an interface that lets you fully control:

1. User Inputs

You can require inputs such as:

• Project description

• Test case

• Tool type

• Additional developer notes

This helps structure experimentation.

2. Agent Behavior Instructions

In the configuration window, you can tell the agent:

• What it’s supposed to simulate

• How it should analyze your tools

• Where to pull relevant information

• How detailed the reasoning should be

Because behavior is unrestricted, you can make the agent extremely specialized with just a few lines of instruction.

3. Adding Custom Tools

This is the core value of this agent.
Developers can add:

• Single tools

• Multiple chained tools

• Placeholder tools

• Data transformers

• API call simulators

• Custom internal utilities

If you want to validate tool order or parameter accuracy, this is the perfect environment.

4. Publish and Test

Once you’re done:

• Click Publish

• Enter a message describing what you want to test

• Run the agent and observe its behavior

The agent will then process your prompt, run your tools, and display a detailed output explaining what it did and why.

What Running the Agent Looks Like

Let’s say you want the agent to help you generate a landing page.
You might type a prompt like:

“Help me plan a landing page for our new consulting service.”

The agent will:

• Read your brand details

• Use product context

• Analyze your instructions

• Then produce a plan for layout, messaging, and visual elements

You can then ask the agent to refine its reasoning further or adjust its recommendations based on your tools or new instructions.

Because you can chat with the agent during testing, you can iterate rapidly like a live debugging session.

Why This Agent Matters for Developers

The Developer Tool Testing Agent makes the development process faster, safer, and more predictable by giving developers:

• A sandbox for experimentation

• A way to validate multi-step workflows

• A debugging environment with transparent reasoning

• A simulation for different agent behaviors

• A platform to test tool logic before releasing anything to end users

Instead of guessing how an agent will behave with your tools, you get real-time feedback and reliable testing support.

Final Thoughts

HubSpot’s Developer Tool Testing Agent is more than a utility—it’s a foundational tool for building, refining, and validating AI-powered experiences inside HubSpot. By offering verbose reasoning, flexible customization, and reliable tool testing, it ensures developers can confidently build sophisticated AI agents that work exactly as intended.

If you’re planning new tools, experimenting with agent behavior, or looking for a safer development workflow, this agent is one of the most valuable resources in your HubSpot AI toolkit.