> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mcpcore.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Testing Tools

> Run your tools with real parameters from the dashboard's Run panel — no AI client needed.

## The Run panel

Every tool has a built-in **Run panel** that lets you execute the tool with custom input and inspect the result in real time. Use it to:

* Verify tool logic before connecting an AI client
* Debug parameter handling
* Inspect the exact JSON structure returned to the AI
* Test edge cases with specific inputs

***

## Running a tool

<Steps>
  <Step title="Open the Run tab">
    In the tool editor, click the **Run** tab (or the play button in the toolbar).
  </Step>

  <Step title="Fill in parameters">
    The Run panel renders a form field for each parameter you've defined. Required parameters are marked.

    Enter real values — the code runs with exactly what you provide.
  </Step>

  <Step title="Click Run tool">
    Click the **Run tool** button. The tool executes in the sandbox with your inputs.
  </Step>

  <Step title="Inspect the result">
    The response section shows:

    * **Return value** — the JSON the AI would receive
    * **Console output** — any `console.log()` / `console.error()` calls your code made
    * **Execution time** — how long the tool took to run
    * **Error** — if the tool threw an exception, the full stack trace
  </Step>
</Steps>

***

## Reading console output

`console.log()`, `console.info()`, `console.warn()`, `console.error()`, and `console.debug()` all appear in the Run panel's **Logs** section during a test run. Use them liberally while developing:

```javascript theme={null}
console.log("Fetching data for user:", params.userId);

const rows = await db.select("orders", { user_id: params.userId });

console.log("Found", rows.length, "orders");

if (rows.length === 0) {
  console.warn("No orders found — returning empty result");
  return { orders: [] };
}

return { orders: rows };
```

***

## Debugging failures

When a tool throws an error, the Run panel shows:

* The error message
* The full stack trace
* The log output that ran before the failure

Common failure patterns:

| Symptom                         | Likely cause                                                        |
| ------------------------------- | ------------------------------------------------------------------- |
| `env.MY_KEY is undefined`       | Secret not added to this server, or key name typo                   |
| `res.status()` is `401` / `403` | Wrong or expired credentials in secret                              |
| `JSON.parse()` throws           | Upstream API returned non-JSON (check `res.body()` in a log)        |
| `db.select()` throws            | Wrong DB host/port/credentials, or table doesn't exist              |
| Execution timeout               | Tool taking > 10s — inspect what step is slow with `console.time()` |

***

## Testing vs production

Runs from the Run panel are **real executions** — they consume API credits, write to databases, and send real requests to external services. Keep this in mind when testing tools that perform write operations or send notifications.

<Note>
  Test runs appear in [Traffic Logs](/observability/traffic-logs) with the source `dashboard-run` so you can distinguish them from AI-initiated calls.
</Note>

***

## Testing with secrets

Secrets (`env.*`) are available during Run panel executions — no special setup needed. The same encrypted values your production code uses are injected into test runs.