The playground
What you will learn The place where you invoke a connected tool directly, without an agent, and when to use it.
After attaching tools, you confirm and test the list from this screen.
Pressing the tool yourself
Attaching an MCP server brings in several tools. But right after attaching, you do not know these things:
The playground is where you check that without a conversation. Pick a tool, argument fields appear, enter values, run it, and the result is shown as-is.
The fields are generated for you
It reads the tool's declared argument specification and draws inputs matching the types.
| Argument type | Input |
|---|---|
| String | text field |
| Number | number field |
| Boolean | toggle |
| One of a fixed set | select list |
| List or object | structured input |
Required arguments are marked too. We said that a poor tool description makes the model get arguments wrong; pressing it here makes that visible.
When to use it
1. Right after attaching a tool
Do not test it for the first time in a conversation. When it fails you cannot tell whether the tool or the model's judgement was at fault. Check here first and tool problems get caught here.
2. To see the size of results
Large results get set aside. Seeing how big a tool's output is in advance tells you whether you need range arguments.
3. To check whether credentials expired
The most common finding in a quarterly review is an expired token. One call in the playground reveals it immediately.
4. When improving a tool description
Calling it yourself clarifies when this tool should be used. Feed that back into the description and the model's selection gets more accurate.
How it differs from a conversation
| Conversation | Playground | |
|---|---|---|
| Who picks the tool | the model | you |
| Who sets the arguments | the model | you |
| On failure | causes are mixed | confirmed to be the tool |
| Purpose | getting work done | checking |
The playground is the tool with the model's judgement removed.
Things to watch
It really executes
Being a test does not make it safe. Press a write tool and it writes.
The tools are permissions perspective applies here too. Do not casually press an irreversible tool, even with test values.
It counts towards usage
Playground calls are recorded in usage as well. Calling large results repeatedly costs accordingly.
Check yourself
1. Why not test a newly attached tool in a conversation?
Answer
Because when it fails you cannot tell whether the tool or the model's judgement was at fault. The playground calls the tool with the model removed, so a failure there is confirmed to be the tool.
2. What is the core difference from a conversation?
Answer
You, not the model, choose the tool and its arguments. It is the tool with the model's judgement taken out.
3. Which tools warrant caution even in testing?
Answer
Irreversible ones — create, send, delete, pay. They really execute in the playground too.
Next, deciding which tools stay on → Turning tools on and off