# Create call

URL: https://docs.hanzo.ai/docs/openapi/tool/post-tool-call

> Runs one of the caller's activated tools and answers with its output.

`POST /v1/tool/call`

> [Tool →](https://docs.hanzo.ai/docs/openapi/tool) · [All API references →](https://docs.hanzo.ai/docs/openapi) · [Get started →](https://docs.hanzo.ai/docs/guides)

|               |                                        |
| ------------- | -------------------------------------- |
| **Address**   | `https://api.hanzo.ai/v1/tool/call`    |
| **Method**    | `POST`                                 |
| **Operation** | `post_tool_call`                       |
| **Auth**      | `Authorization: Bearer $HANZO_API_KEY` |

Runs one of the caller's activated tools and answers with its output.

This is the endpoint onto the tool plane's DYNAMIC half — the half no build-time
catalogue can hold, because it is per-tenant: an org's connected connector
actions, its authored skills, its agents and functions, and the tools of every
external MCP server it registered. A tool's existence, its price and its
activation are all rows, not code, so they cannot be known until the caller is.

One policy, the registry's: resolve by precedence, refuse an unactivated tool
403, settle a priced one through the x402 client or fail closed 402, then
dispatch to the winning source bound to the caller's own (org, project). One
metered unit, one audit record. A caller can only ever dispatch its own tools.

Discovery is GET /v1/tool — ?activated=true for the callable set.

## Request

3 fields, body `application/json` (required).

| Field         | In   | Type   | Required | Description                                                                                    |
| ------------- | ---- | ------ | -------- | ---------------------------------------------------------------------------------------------- |
| `arguments`   | body | object | —        | Arguments is the tool's own input object, passed through verbatim to whichever source owns it. |
| `arguments.*` | body | any    | —        |                                                                                                |
| `name`        | body | string | —        | Name is the tool to run, exactly as GET /v1/tool reports it.                                   |

## Response

| Status    | Body            | Meaning |
| --------- | --------------- | ------- |
| `200`     | tool.toolResult | ok      |
| `default` | problem-details | refused |

`200` body — 2 fields.

| Field    | In   | Type   | Always | Description                                                                            |
| -------- | ---- | ------ | ------ | -------------------------------------------------------------------------------------- |
| `name`   | body | string | —      | Name is the tool that ran.                                                             |
| `result` | body | any    | —      | Result is the tool's own output, verbatim — its shape is the tool's, not this plane's. |

Failure carries the platform error shape — see [Errors](https://docs.hanzo.ai/docs/errors).

## Examples

**CLI**

```bash
hanzo tool call
```

**SDK**

**.ts**

```ts
import { Configuration, ToolApi } from 'hanzoai';

const api = new ToolApi(new Configuration({ accessToken: process.env.HANZO_API_KEY }));
const { data } = await api.postToolCall({ arguments: {}, name: "<name>" });
```

**.py**

```python
from hanzoai.cloud import ApiClient, Configuration
from hanzoai.cloud.api import ToolApi

client = ApiClient(Configuration(access_token=os.environ["HANZO_API_KEY"]))
result = ToolApi(client).post_tool_call(arguments={}, name="<name>")
```

**.go**

```go
cfg := hanzoai.NewConfiguration()
cfg.AddDefaultHeader("Authorization", "Bearer "+os.Getenv("HANZO_API_KEY"))
client := hanzoai.NewAPIClient(cfg)

resp, _, err := client.ToolAPI.PostToolCall(context.Background()).Execute()
if err != nil {
	return err
}
```

**.rs**

```rust
use hanzo_client::apis::{configuration::Configuration, tool_api};

let mut cfg = Configuration::new();
cfg.bearer_access_token = std::env::var("HANZO_API_KEY").ok();

let result = tool_api::post_tool_call(&cfg, Default::default()).await?;
```

**.java**

```java
import ai.hanzo.cloud.ApiClient;
import ai.hanzo.cloud.api.ToolApi;

ApiClient client = new ApiClient();
client.setBearerToken(System.getenv("HANZO_API_KEY"));

var result = new ToolApi(client).postToolCall();
```

**HTTP**

```bash
curl -X POST https://api.hanzo.ai/v1/tool/call \
  -H "Authorization: Bearer $HANZO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
       "arguments": {},
       "name": "<name>"
     }'
```

**MCP**

MCP reaches **tool** through the `tool` tool, which names its 17 operations with its own verbs — this one among them, under a name only MCP declares. `describe` explains any of them:

```bash
curl -X POST https://api.hanzo.ai/v1/mcp \
  -H "Content-Type: application/json" \
  -d '{
       "jsonrpc": "2.0",
       "id": 1,
       "method": "tools/call",
       "params": {
         "name": "describe",
         "arguments": {
           "op": "list_tools"
         }
       }
     }'
```

---

[Tool API](https://docs.hanzo.ai/docs/openapi/tool) · [All Hanzo APIs](https://docs.hanzo.ai/docs/openapi) · [Interactive reference](https://docs.hanzo.ai/docs/openapi/reference)