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

# Tool Server Protocol

> HTTP interface that all tool servers expose

Every tool server (coding, email, calendar, etc.) exposes the same HTTP interface. This is what agents interact with at runtime.

**Base URL:** Provided per-task in the `tool_servers` field of the task response.

## List Tools

Get available tools and their parameter schemas.

```
GET /tools
```

**Response:** `200 OK`

```json theme={null}
{
  "tools": [
    {
      "name": "send_email",
      "description": "Send an email to the specified recipient.",
      "parameters": {
        "type": "object",
        "properties": {
          "to": { "type": "string", "description": "Recipient email address" },
          "subject": { "type": "string", "description": "Email subject line" },
          "body": { "type": "string", "description": "Email body text" }
        },
        "required": ["to", "subject", "body"]
      }
    }
  ]
}
```

## Execute a Tool

Invoke a tool action and get the result.

```
POST /step
```

**Request body:**

```json theme={null}
{
  "action": {
    "tool_name": "send_email",
    "parameters": {
      "to": "candidate@example.com",
      "subject": "Interview Scheduling",
      "body": "Hello, we'd like to schedule..."
    }
  }
}
```

**Response:** `200 OK`

```json theme={null}
{
  "observation": "Email sent successfully to candidate@example.com"
}
```

**Error response:**

```json theme={null}
{
  "observation": "Error: invalid email address format",
  "is_error": true
}
```