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The Web Search tool allows LLMs to search the web and retrieve information from web pages. This tool is supported for OpenAI and Gemini providers, enabling models to access real-time information from the internet.

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Overview

The Web Search tool enables models to:
  • Search the web for information
  • Open and read specific web pages
  • Find specific content within web pages
When a model uses the web search tool, it can retrieve up-to-date information that wasn’t part of its training data, making it ideal for queries about current events, recent developments, or specific web content.

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Defining the Web Search Tool

To enable web search capabilities, add the WebSearchTool to your request’s Tools array: 
import (
    "github.com/hastekit/hastekit-sdk-go/pkg/gateway/llm/responses"
    "github.com/hastekit/hastekit-sdk-go/pkg/utils"
)

webSearchTool := responses.ToolUnion{
    OfWebSearch: &responses.WebSearchTool{
        Type:              "web_search",
        Filters:           nil,                        // Optional domain filters
        UserLocation:      nil,                        // Optional user location
        ExternalWebAccess: utils.Ptr(true),           // Enable external web access
        SearchContextSize: utils.Ptr("medium"),       // "low", "medium", or "high"
    },
}

​
Tool Parameters

ParameterTypeDescription
TypestringAlways "web_search"
Filters*WebSearchToolFiltersOptional domain filtering configuration
UserLocation*WebSearchToolUserLocationOptional user location for localized results
ExternalWebAccess*boolWhether to allow access to external websites (default: true)
SearchContextSize*stringAmount of context to retrieve: "low", "medium", or "high" (default: "medium")

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Domain Filtering

You can restrict web searches to specific domains using the Filters parameter: 
webSearchTool := responses.ToolUnion{
    OfWebSearch: &responses.WebSearchTool{
        Type: "web_search",
        Filters: &responses.WebSearchToolFilters{
            AllowedDomains: []string{
                "example.com",
                "docs.example.com",
            },
        },
    },
}

​
User Location

Specify the user’s location to get localized search results: 
webSearchTool := responses.ToolUnion{
    OfWebSearch: &responses.WebSearchTool{
        Type: "web_search",
        UserLocation: &responses.WebSearchToolUserLocation{
            Type:     "location",
            Country:  "US",
            City:     "San Francisco",
            Region:   "CA",
            Timezone: "America/Los_Angeles",
        },
    },
}
Include the web search tool in your request: 
resp, err := client.NewResponses(ctx, &responses.Request{
    Model: "OpenAI/gpt-4.1-mini",
    Input: responses.InputUnion{
        OfString: utils.Ptr("What are the latest developments in AI?"),
    },
    Tools: []responses.ToolUnion{webSearchTool},
})

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Handling Web Search Calls

When the model decides to use web search, it will return a WebSearchCallMessage in the response output. You can detect and process these calls: 
for _, output := range resp.Output {
    if output.OfWebSearchCall != nil {
        webSearchCall := output.OfWebSearchCall
        
        fmt.Printf("Web Search ID: %s\n", webSearchCall.ID)
        fmt.Printf("Status: %s\n", webSearchCall.Status)
        
        // Handle different action types
        if webSearchCall.Action.OfSearch != nil {
            searchAction := webSearchCall.Action.OfSearch
            fmt.Printf("Search Query: %s\n", searchAction.Query)
            fmt.Printf("Queries: %v\n", searchAction.Queries)
            
            // Process search results
            for _, source := range searchAction.Sources {
                fmt.Printf("Source URL: %s\n", source.URL)
            }
        } else if webSearchCall.Action.OfOpenPage != nil {
            openPageAction := webSearchCall.Action.OfOpenPage
            fmt.Printf("Opening page: %s\n", openPageAction.URL)
        } else if webSearchCall.Action.OfFind != nil {
            findAction := webSearchCall.Action.OfFind
            fmt.Printf("Finding pattern '%s' in %s\n", findAction.Pattern, findAction.URL)
        }
    }
}

​
Web Search Action Types

The web search tool supports three types of actions:

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1. Search Action

Performs a web search query: 
type WebSearchCallActionOfSearch struct {
    Type    string   `json:"type"`    // "search"
    Query   string   `json:"query"`   // Main search query
    Queries []string `json:"queries"` // Alternative queries
    Sources []WebSearchCallActionOfSearchSource `json:"sources"`
}

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2. Open Page Action

Opens and reads a specific web page: 
type WebSearchCallActionOfOpenPage struct {
    Type string `json:"type"` // "open_page"
    URL  string `json:"url"`   // URL to open
}

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3. Find Action

Searches for specific content within a web page: 
type WebSearchCallActionOfFind struct {
    Type    string `json:"type"`    // "find"
    URL     string `json:"url"`     // URL to search within
    Pattern string `json:"pattern"` // Pattern to find
}

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Streaming Web Search Calls

When using streaming responses, web search calls are delivered through specific chunk types: 
stream, err := client.NewStreamingResponses(ctx, &responses.Request{
    Model: "OpenAI/gpt-4.1-mini",
    Input: responses.InputUnion{
        OfString: utils.Ptr("What's happening in the tech world today?"),
    },
    Tools: []responses.ToolUnion{webSearchTool},
})

for chunk := range stream {
    switch chunk.ChunkType() {
    case "response.web_search_call.in_progress":
        // Web search has started
        fmt.Println("Web search initiated")
        
    case "response.web_search_call.searching":
        // Search is in progress
        fmt.Println("Searching the web...")
        
    case "response.web_search_call.completed":
        // Search completed
        fmt.Println("Web search completed")
        
    case "response.output_item.done":
        // Check if the completed item is a web search call
        if chunk.OfOutputItemDone.Item.Type == "web_search_call" {
            item := chunk.OfOutputItemDone.Item
            if item.Action != nil && item.Action.OfSearch != nil {
                searchAction := item.Action.OfSearch
                fmt.Printf("Search query: %s\n", searchAction.Query)
                
                // Process search results
                for _, source := range searchAction.Sources {
                    fmt.Printf("Found: %s\n", source.URL)
                }
            }
        }
    }
}

​
Complete Example

Here’s a complete example demonstrating web search usage: 
package main

import (
    "context"
    "fmt"
    "log"
    "os"

    "github.com/hastekit/hastekit-sdk-go/pkg/utils"
    "github.com/hastekit/hastekit-sdk-go/pkg/gateway"
    "github.com/hastekit/hastekit-sdk-go/pkg/gateway/llm"
    "github.com/hastekit/hastekit-sdk-go/pkg/gateway/llm/responses"
    hastekit "github.com/hastekit/hastekit-sdk-go"
)

func main() {
    client, err := hastekit.New(&hastekit.ClientOptions{
        ProviderConfigs: []gateway.ProviderConfig{
            {
                ProviderName:  llm.ProviderNameOpenAI,
                BaseURL:       "",
                CustomHeaders: nil,
                ApiKeys: []*gateway.APIKeyConfig{
                    {
                        Name:   "Key 1",
                        APIKey: os.Getenv("OPENAI_API_KEY"),
                    },
                },
            },
        },
    })
    if err != nil {
        log.Fatal(err)
    }

    // Define web search tool
    webSearchTool := responses.ToolUnion{
        OfWebSearch: &responses.WebSearchTool{
            Type:              "web_search",
            ExternalWebAccess: utils.Ptr(true),
            SearchContextSize: utils.Ptr("medium"),
        },
    }

    // Make request with web search
    resp, err := client.NewResponses(context.Background(), &responses.Request{
        Model: "OpenAI/gpt-4o",
        Input: responses.InputUnion{
            OfString: utils.Ptr("What are the latest news about artificial intelligence?"),
        },
        Tools: []responses.ToolUnion{webSearchTool},
    })
    if err != nil {
        log.Fatal(err)
    }

    // Process response
    for _, output := range resp.Output {
        if output.OfWebSearchCall != nil {
            fmt.Printf("Web search performed: %s\n", output.OfWebSearchCall.ID)
            if output.OfWebSearchCall.Action.OfSearch != nil {
                fmt.Printf("Query: %s\n", output.OfWebSearchCall.Action.OfSearch.Query)
            }
        } else if output.OfOutputMessage != nil {
            // Model's response using the search results
            fmt.Println(output.OfOutputMessage.Content[0].OfOutputText.Text)
        }
    }
}

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Provider Support

The Web Search tool is supported by the following providers:
ProviderSupport
OpenAI✅
Gemini❌
Anthropic✅
xAI❌
Ollama❌

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Best Practices

  1. Use appropriate search context size: Choose "low" for quick searches, "medium" for balanced results, or "high" for comprehensive information.
  2. Domain filtering: When you need information from specific sources, use domain filters to ensure the model only searches within trusted domains.
  3. User location: Specify user location when you need localized results (e.g., local news, regional information).
  4. Error handling: Always check the Status field of WebSearchCallMessage to handle cases where the search might have failed.
  5. Streaming: For better user experience, use streaming responses to show search progress in real-time.

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Limitations

  • Web search results depend on the search engine’s capabilities and may vary by provider
  • Some websites may block automated access
  • Search results may not always be up-to-date or accurate
  • Rate limits may apply depending on your provider and plan