Specialist Routing (Domain Expertise)

Overview

No model is the best at everything. Some excel at coding, others at creative writing, medical terminology, or mathematical reasoning. Specialist routing ensures every request goes to the model that’s best-in-class for that specific domain.

The Problem

Using a single “jack-of-all-trades” model means:

Coding questions get generic responses instead of precise, syntax-aware answers
Creative writing lacks the nuance and style of specialized creative models
Medical queries miss domain-specific terminology and accuracy
Mathematical problems lack the reasoning capabilities of math-optimized models

You’re settling for average performance across all domains instead of excellence in each.

The Solution

A specialist router detects the domain of each request and routes it to the best model for that specific task:

Python coding question → Gemini 2.5 Flash or GPT-5 (coding-optimized)
Poetic brand description → Claude Opus 4 (creative writing)
Medical diagnosis query → Specialized medical LLM or Claude (medical knowledge)
Mathematical proof → Models optimized for mathematical reasoning

How It Works

Request arrives with domain-specific content
Inworld Router analyzes the prompt to detect domain (coding, creative, medical, math, etc.)
Inworld Router routes to the model optimized for that domain
Response is returned with best-in-class quality for that specific niche

Implementation

Step 1: Create a Specialist Router

Create a router with domain-specific routes using conditional routing:

curl --request POST \
  --url https://api.inworld.ai/router/v1/routers \
  --header 'Authorization: Bearer <your-api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
    "name": "routers/specialist-routing",
    "defaults": {
      "text_generation_config": {
        "max_new_tokens": 1024,
        "temperature": 0.7
      }
    },
    "routes": [
      {
        "route": {
          "route_id": "coding-specialist",
          "variants": [
            {
              "variant": {
                "variant_id": "gemini-flash-coding",
                "model_id": "google-ai-studio/gemini-2.5-flash"
              },
              "weight": 60
            },
            {
              "variant": {
                "variant_id": "gpt5-coding",
                "model_id": "openai/gpt-5"
              },
              "weight": 40
            }
          ]
        },
        "condition": {
          "cel_expression": "domain == \"coding\""
        }
      },
      {
        "route": {
          "route_id": "creative-specialist",
          "variants": [
            {
              "variant": {
                "variant_id": "claude-creative",
                "model_id": "anthropic/claude-opus-4-20250514"
              },
              "weight": 70
            },
            {
              "variant": {
                "variant_id": "gpt5-creative",
                "model_id": "openai/gpt-5"
              },
              "weight": 30
            }
          ]
        },
        "condition": {
          "cel_expression": "domain == \"creative\""
        }
      },
      {
        "route": {
          "route_id": "math-specialist",
          "variants": [
            {
              "variant": {
                "variant_id": "o3-math",
                "model_id": "openai/o3-mini"
              },
              "weight": 60
            },
            {
              "variant": {
                "variant_id": "gemini-math",
                "model_id": "google-ai-studio/gemini-2.5-flash"
              },
              "weight": 40
            }
          ]
        },
        "condition": {
          "cel_expression": "domain == \"math\""
        }
      },
      {
        "route": {
          "route_id": "general-purpose",
          "variants": [
            {
              "variant": {
                "variant_id": "gpt5-general",
                "model_id": "openai/gpt-5"
              },
              "weight": 60
            },
            {
              "variant": {
                "variant_id": "claude-general",
                "model_id": "anthropic/claude-opus-4-6"
              },
              "weight": 40
            }
          ]
        },
        "condition": {
          "cel_expression": "domain == \"general\" || domain == \"\""
        }
      }
    ],
    "defaultRoute": {
      "route_id": "default",
      "variants": [
        {
          "variant": {
            "variant_id": "default-general",
            "model_id": "openai/gpt-5"
          },
          "weight": 100
        }
      ]
    }
  }'

Model IDs are specified as strings in the format "provider/model" (e.g., "openai/gpt-5"). Routes use CEL expressions to match based on domain. Routes are evaluated in order, and the first matching route is selected. Weights must sum to exactly 100 within each route - they are not normalized and are independent per route.

Step 2: Use Domain-Specific Routing

Pass the domain in extra_body.metadata to route requests:

# Route coding questions to coding specialists
curl --location 'https://api.inworld.ai/v1/chat/completions' \
--header 'Authorization: Bearer <your-api-key>' \
--header 'Content-Type: application/json' \
--data '{
  "model": "inworld/specialist-routing",
  "messages": [
    {"role": "user", "content": "Write a Python function to implement quicksort with detailed comments"}
  ],
  "extra_body": {
    "metadata": {
      "domain": "coding"
    }
  }
}'

# Route creative requests to creative specialists
curl --location 'https://api.inworld.ai/v1/chat/completions' \
--header 'Authorization: Bearer <your-api-key>' \
--header 'Content-Type: application/json' \
--data '{
  "model": "inworld/specialist-routing",
  "messages": [
    {"role": "user", "content": "Write a poetic brand description for a sustainable fashion company that emphasizes craftsmanship and environmental consciousness"}
  ],
  "extra_body": {
    "metadata": {
      "domain": "creative"
    }
  }
}'

# Route math problems to math specialists
curl --location 'https://api.inworld.ai/v1/chat/completions' \
--header 'Authorization: Bearer <your-api-key>' \
--header 'Content-Type: application/json' \
--data '{
  "model": "inworld/specialist-routing",
  "messages": [
    {"role": "user", "content": "Prove that the square root of 2 is irrational"}
  ],
  "extra_body": {
    "metadata": {
      "domain": "math"
    }
  }
}'

Domain-Specific Model Selection

Coding Tasks

Use models optimized for code generation and understanding:

Gemini 2.5 Flash: Fast and capable code generation across multiple languages
GPT-5: Excellent coding capabilities with broad language support
Claude Opus 4: Strong code understanding and generation

Sort criteria: ["coding", "intelligence"]

Creative Writing

Use models with strong creative and stylistic capabilities:

Claude Opus 4: Exceptional creative writing and nuanced responses
GPT-5: Strong creative capabilities with good style variation
Gemini Pro: Good creative writing with diverse styles

Sort criteria: ["intelligence"]

Mathematical Reasoning

Use models optimized for mathematical problem-solving:

o3-mini: OpenAI’s reasoning model optimized for math
Gemini 2.5 Flash: Strong mathematical reasoning capabilities
Claude Opus 4: Excellent mathematical problem-solving

Sort criteria: ["math", "intelligence"]

Medical & Scientific

Use models with strong domain knowledge:

Claude Opus 4: Excellent medical and scientific knowledge
GPT-5: Strong domain knowledge across medical and scientific fields
Specialized medical LLMs: For highly specialized medical queries

Sort criteria: ["intelligence"] (domain knowledge is typically part of general intelligence)

General Purpose

For queries that don’t fit a specific domain:

GPT-5: Best overall general-purpose model
Claude Opus 4: Excellent general-purpose capabilities
Gemini 2.5 Flash: Fast and capable general-purpose option

Sort criteria: ["intelligence", "price"]

Advanced: Prompt-Based Domain Detection

For more sophisticated routing, use system prompts to classify domains:

{
  "defaults": {
    "message_templates": [
      {
        "role": "system",
        "content": "You are a domain classifier. Analyze the user's query and classify it as one of: 'coding', 'creative', 'math', 'medical', 'general'. Respond with only the domain name."
      }
    ]
  }
}

Then use the classification result to route to the appropriate specialist model.

Use Cases

Software Development Platform

Route code-related queries to coding specialists:

# Code generation
curl --location 'https://api.inworld.ai/v1/chat/completions' \
  --header 'Authorization: Bearer <your-api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "model": "inworld/specialist-routing",
  "messages": [{"role": "user", "content": "Implement a REST API endpoint in Node.js"}],
  "extra_body": {"sort": ["coding"]}
}'

# Code review
curl --location 'https://api.inworld.ai/v1/chat/completions' \
  --header 'Authorization: Bearer <your-api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "model": "inworld/specialist-routing",
  "messages": [{"role": "user", "content": "Review this Python code for performance issues"}],
  "extra_body": {"sort": ["coding"]}
}'

Content Creation Platform

Route creative requests to creative specialists:

# Brand copywriting
curl --location 'https://api.inworld.ai/v1/chat/completions' \
  --header 'Authorization: Bearer <your-api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "model": "inworld/specialist-routing",
  "messages": [{"role": "user", "content": "Write compelling product descriptions for an e-commerce site"}],
  "extra_body": {"sort": ["intelligence"]}
}'

Educational Platform

Route math problems to math specialists:

# Mathematical proofs
curl --location 'https://api.inworld.ai/v1/chat/completions' \
  --header 'Authorization: Bearer <your-api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "model": "inworld/specialist-routing",
  "messages": [{"role": "user", "content": "Prove that the square root of 2 is irrational"}],
  "extra_body": {"sort": ["math"]}
}'

Advanced: Domain Pattern Matching

You can use CEL string operations for more flexible domain matching:

Domain Prefix Matching

Route multiple related domains using pattern matching:

{
  "route": {
    "route_id": "coding-variants",
    "variants": [...]
  },
  "condition": {
    "cel_expression": "domain.startsWith('code') || domain.contains('programming') || domain.contains('debug')"
  }
}

This routes coding, programming, and debugging requests to coding specialists.

Domain + Complexity Routing

Route complex domain-specific tasks to premium models:

{
  "route": {
    "route_id": "complex-coding",
    "variants": [...]
  },
  "condition": {
    "cel_expression": "domain == \"coding\" && complexity_score >= 8"
  }
}

This ensures complex coding tasks get premium models while simple coding tasks use cost-effective options.

Multiple Domain Support

Route to the same specialist for multiple related domains:

{
  "route": {
    "route_id": "coding-specialist",
    "variants": [...]
  },
  "condition": {
    "cel_expression": "domain == \"coding\" || domain == \"debugging\" || domain == \"refactoring\" || domain == \"code-review\""
  }
}

This consolidates multiple coding-related domains into a single specialist route.

Domain + Content Length

Route long-form domain content to appropriate models:

{
  "route": {
    "route_id": "long-creative",
    "variants": [...]
  },
  "condition": {
    "cel_expression": "domain == \"creative\" && content_length > 5000"
  }
}

This routes long creative writing tasks to models optimized for extended content generation.

Best Practices

Map domains to models: Create a clear mapping of domains to optimal models
Test domain detection: Ensure your routing logic correctly identifies domains
Monitor quality: Track response quality per domain to optimize routing
Fallback to general: Always have a general-purpose route as fallback
Update regularly: As new specialized models emerge, update your routing
Use pattern matching: Leverage CEL string operations (startsWith, contains, endsWith) for flexible domain matching
Combine factors: Use complexity scores and content length to refine routing decisions

Performance Benefits

Specialist routing provides:

Higher quality: Best-in-class responses for each domain
Better user experience: Users get expert-level answers in their domain
Cost optimization: Use specialized models only when needed
Competitive advantage: Superior quality compared to single-model approaches

Next Steps

Learn about cost optimization to reduce API costs
Explore failover routing for high availability
Review model selection criteria for available options

Getting Started

Core Concepts

Migration

Resources

Overview

The Problem

The Solution

How It Works

Implementation

Step 1: Create a Specialist Router

Step 2: Use Domain-Specific Routing

Domain-Specific Model Selection

Coding Tasks

Creative Writing

Mathematical Reasoning

Medical & Scientific

General Purpose

Advanced: Prompt-Based Domain Detection

Use Cases

Software Development Platform

Content Creation Platform

Educational Platform

Advanced: Domain Pattern Matching

Domain Prefix Matching

Domain + Complexity Routing

Multiple Domain Support

Domain + Content Length

Best Practices

Performance Benefits

Next Steps

​Overview

​The Problem

​The Solution

​How It Works

​Implementation

​Step 1: Create a Specialist Router

​Step 2: Use Domain-Specific Routing

​Domain-Specific Model Selection

​Coding Tasks

​Creative Writing

​Mathematical Reasoning

​Medical & Scientific

​General Purpose

​Advanced: Prompt-Based Domain Detection

​Use Cases

​Software Development Platform

​Content Creation Platform

​Educational Platform

​Advanced: Domain Pattern Matching

​Domain Prefix Matching

​Domain + Complexity Routing

​Multiple Domain Support

​Domain + Content Length

​Best Practices

​Performance Benefits

​Next Steps

Overview

The Problem

The Solution

How It Works

Implementation

Step 1: Create a Specialist Router

Step 2: Use Domain-Specific Routing

Domain-Specific Model Selection

Coding Tasks

Creative Writing

Mathematical Reasoning

Medical & Scientific

General Purpose

Advanced: Prompt-Based Domain Detection

Use Cases

Software Development Platform

Content Creation Platform

Educational Platform

Advanced: Domain Pattern Matching

Domain Prefix Matching

Domain + Complexity Routing

Multiple Domain Support

Domain + Content Length

Best Practices

Performance Benefits

Next Steps