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Server tools are tools that Phaseo runs for you during a model request. The model decides when to call them, Phaseo executes the tool server-side, and the tool result is fed back into the model loop. Use server tools when the model needs current time, web context, fetched page text, or a second model’s advice without adding your own tool executor.
Server tools are in beta. Request shapes and result payloads may evolve as provider support changes.

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Available tools

ToolTypeUse it for
Datetimegateway:datetimeCurrent date and time in up to 5 timezones
Web Searchphaseo:web_searchModel-directed web searches during a request
Web Fetchphaseo:web_fetchFetching and extracting text from specific URLs
Advisorphaseo:advisorConsulting another model mid-generation
Subagentphaseo:subagentDelegating focused work to a worker model
FusionAdvisor workflowConsulting several advisor models and an optional judge
Image Generationphaseo:image_generationCreating images from the model tool loop

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How server tools work

  1. Add one or more server tools to the tools array.
  2. The model decides whether it needs a tool and emits a tool call.
  3. Phaseo intercepts the server-tool call, executes it, and sends the result back to the model.
  4. The model continues and writes the final response.
Server tools can be used alongside your own function tools. Phaseo executes only the server tools; your application still handles regular function tool calls.

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Quick start

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 are the latest AI policy updates this week?" }
    ],
    "tools": [
      { "type": "phaseo:web_search" },
      { "type": "gateway:datetime", "parameters": { "timezones": ["Europe/London", "UTC"] } }
    ]
  }'

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Combining with function tools

{
  "model": "openai/gpt-5-nano",
  "messages": [
    { "role": "user", "content": "Find recent funding news and save the best item." }
  ],
  "tools": [
    { "type": "phaseo:web_search", "parameters": { "max_results": 3 } },
    {
      "type": "function",
      "function": {
        "name": "save_research_item",
        "description": "Save a selected research item",
        "parameters": {
          "type": "object",
          "properties": {
            "title": { "type": "string" },
            "url": { "type": "string" }
          },
          "required": ["title", "url"]
        }
      }
    }
  ]
}
If the model calls phaseo:web_search, Phaseo executes that call automatically. If it calls save_research_item, your application receives the function call and must return the function result in a follow-up request.

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Supported endpoints

Server tools are supported on:
  • /v1/chat/completions
  • /v1/responses
  • /v1/messages
Streaming requests are supported. For gateway-managed server tools, Phaseo may materialize the upstream tool-call turn, execute the server tool, continue the loop, and emit a synthetic stream for the final response.

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Usage tracking

Server-tool usage is reported in usage.server_tool_use: 
{
  "usage": {
    "input_tokens": 105,
    "output_tokens": 250,
    "server_tool_use": {
      "datetime_requests": 1,
      "web_search_requests": 2,
      "web_search_results": 8,
      "web_fetch_requests": 1,
      "advisor_requests": 1,
      "subagent_requests": 1,
      "image_generation_requests": 1
    }
  }
}
Pricing can also use server-tool meters such as server_tool_web_search_requests, server_tool_web_search_extra_results, server_tool_web_fetch_requests, server_tool_advisor_requests, server_tool_image_generation_requests, native_web_search_requests, and native_web_fetch_requests when configured on model price cards.

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Tool pages

Datetime

Give the model the current date and time.

Web Search

Let the model search the web when it needs current information.

Web Fetch

Let the model fetch and read specific URLs.

Advisor

Let one model consult another model for guidance mid-generation.

Subagent

Let the model delegate focused tasks to a worker model.

Fusion

Let the Playground configure several advisor models for one answer.

Image Generation

Let the model create images while answering.
Last modified on July 9, 2026