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

# Web Search Server Tool

> Let models search the web during a request.

Use `phaseo:web_search` when the model needs current or source-backed information. The model decides when to search, writes the query, and can search multiple times in one request.

Phaseo returns URLs, titles, snippets, highlights, and optional page text to the model so it can write a grounded response.

<Note>
  Google native web search is not enabled in Phaseo server tools yet. Use managed search or provider-native search on supported OpenAI and Anthropic routes.
</Note>

## How it works

1. Add `{ "type": "phaseo:web_search" }` to `tools`.
2. The model decides whether it needs a search and emits a query.
3. Phaseo executes the search using the configured engine.
4. Results are returned to the model as tool context.
5. The model writes the final response and may search again if needed.

## Quick start

```bash theme={null}
curl https://api.phaseo.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-5-nano",
    "messages": [
      { "role": "user", "content": "What were the major AI announcements this week?" }
    ],
    "tools": [
      { "type": "phaseo:web_search" }
    ]
  }'
```

## Configuration

```json theme={null}
{
  "type": "phaseo:web_search",
  "parameters": {
    "engine": "exa",
    "max_results": 5,
    "max_total_results": 15,
    "search_context_size": "medium",
    "max_characters": 2048,
    "allowed_domains": ["arxiv.org", "nature.com"],
    "excluded_domains": ["reddit.com"],
    "include_highlights": true,
    "include_text": false
  }
}
```

| Parameter             | Type      | Default        | Description                                                                         |
| --------------------- | --------- | -------------- | ----------------------------------------------------------------------------------- |
| `engine`              | string    | `exa`          | Search engine: `auto`, `native`, `exa`, `parallel`, `firecrawl`, or `perplexity`.   |
| `max_results`         | integer   | `5`            | Maximum results returned per search call.                                           |
| `max_total_results`   | integer   | `10`           | Maximum cumulative results across the server-tool loop.                             |
| `search_context_size` | string    | `medium`       | Context size for engines that support highlight sizing: `low`, `medium`, or `high`. |
| `max_characters`      | integer   | engine default | Maximum text characters per result when text is included.                           |
| `allowed_domains`     | string\[] | none           | Only return results from these domains. Alias: `include_domains`.                   |
| `excluded_domains`    | string\[] | none           | Exclude results from these domains. Alias: `exclude_domains`.                       |
| `include_highlights`  | boolean   | `true`         | Include engine-provided highlights/snippets when available.                         |
| `include_text`        | boolean   | `false`        | Include fuller result text when the engine supports it.                             |
| `user_location`       | object    | none           | Optional location hint for engines that support localized search.                   |

## Engine selection

| Engine       | Behavior                                                                                                                                                                                          |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `exa`        | Managed Exa search. Requires Phaseo to have Exa configured for the gateway runtime.                                                                                                               |
| `auto`       | Uses the configured managed default, currently Exa.                                                                                                                                               |
| `parallel`   | Uses Parallel search when configured.                                                                                                                                                             |
| `firecrawl`  | Uses Firecrawl search when configured.                                                                                                                                                            |
| `perplexity` | Uses the first-party Perplexity Search API when configured. Supports ranked results, `search_context_size`, regional search from `user_location.country`, and either allowed or excluded domains. |
| `native`     | Converts the declaration to a provider-native web-search tool before the upstream model call when the request surface supports it.                                                                |

Use `engine: "native"` only in the tool declaration. If a model tries to pass `engine: "native"` inside an already-emitted gateway search call, Phaseo returns a tool error because native tools must be selected before the upstream request is sent.

## Domain filtering

Use `allowed_domains` when the answer must come from a controlled source set:

```json theme={null}
{
  "type": "phaseo:web_search",
  "parameters": {
    "allowed_domains": ["phaseo.app", "github.com"]
  }
}
```

Use `excluded_domains` when broad web search is allowed but specific domains should be removed from the result set.

Perplexity and Firecrawl accept either `allowed_domains` or `excluded_domains` in a single search call, not both. Perplexity accepts up to 20 domain filters per request and maps excluded domains to its denylist format.

## Responses API

The same tool shape works with `/v1/responses`:

```json theme={null}
{
  "model": "openai/gpt-5-nano",
  "input": "Find the latest release notes for Phaseo.",
  "tools": [
    { "type": "phaseo:web_search", "parameters": { "max_results": 4 } }
  ]
}
```

## Usage and pricing

Web search calls increment:

```json theme={null}
{
  "usage": {
    "server_tool_use": {
      "web_search_requests": 1,
      "web_search_results": 5,
      "web_search_extra_results": 0
    }
  }
}
```

Managed search pricing can use `server_tool_web_search_requests` and `server_tool_web_search_extra_results`. Provider-native search usage can use `native_web_search_requests` where a model price card defines that meter.

## Related

* [Web Fetch](./web-fetch)
* [Server Tools](./index)
* [Tool grounding with web fetch](../../cookbook/tool-grounding-with-web-fetch)