Agent Selecting Models

Selecting AI Models for Agents

Guidelines for choosing between sonnet and haiku models based on agent capabilities and task requirements.

When This Skill Loads

This Skill auto-loads when implementing agents or documenting model selection rationale.

Available Models

Sonnet (claude-sonnet-4-5)

Characteristics:

• Advanced reasoning capabilities
• Complex decision-making
• Deep pattern recognition
• Sophisticated analysis
• Multi-step orchestration
• Higher cost, slower performance

Use for: Complex, reasoning-intensive tasks

Haiku (claude-haiku-3-5)

Characteristics:

• Fast execution
• Straightforward tasks
• Pattern matching
• Simple decision-making
• Cost-effective
• Lower cost, faster performance

Use for: Simple, well-defined tasks

Decision Framework

Use Sonnet When Task Requires:

✅ Advanced Reasoning

• Analyzing technical claims for subtle contradictions
• Distinguishing objective errors from subjective improvements
• Detecting false positives in validation findings
• Context-dependent decision-making
• Inferring user intent from ambiguous requests

✅ Complex Pattern Recognition

• Cross-referencing multiple documentation files
• Identifying conceptual duplications (not just verbatim)
• Detecting inconsistencies across architectural layers
• Understanding domain-specific patterns
• Recognizing semantic similarities

✅ Sophisticated Analysis

• Verifying factual accuracy against authoritative sources
• Assessing confidence levels (HIGH/MEDIUM/FALSE_POSITIVE)
• Evaluating code quality and architectural decisions
• Analyzing narrative flow and pedagogical structure
• Determining fix safety and impact

✅ Multi-Step Orchestration

• Coordinating complex validation workflows
• Managing dependencies between validation steps
• Iterative refinement processes
• Dynamic workflow adaptation
• Error recovery and retry logic

✅ Deep Web Research

• Finding and evaluating authoritative sources
• Comparing claims against official documentation
• Version verification across multiple registries
• API correctness validation
• Detecting outdated information

Use Haiku When Task Is:

✅ Pattern Matching

• Extracting URLs from markdown files
• Finding code blocks by language
• Matching file naming patterns
• Regular expression searches
• Simple syntax validation

✅ Sequential Execution

• File existence checks
• URL accessibility validation
• Cache file reading/writing
• Date comparisons
• Status reporting

✅ Straightforward Validation

• Checking if files exist
• Verifying link format (contains .md)
• Counting lines or characters
• Comparing timestamps
• Simple YAML/JSON parsing

✅ No Complex Reasoning

• Tasks with clear pass/fail criteria
• No ambiguity or judgment required
• Deterministic outcomes
• No context analysis needed
• No trade-off decisions

✅ High-Volume Processing

• Checking hundreds of links
• Validating many files
• Batch operations
• Performance-critical tasks
• Cost-sensitive operations

Model Selection Matrix

Agent-Specific Examples

Sonnet Examples

docs-checker (Complex validation):

model: sonnet

Reasoning:

• Analyzes technical claims for contradictions
• Deep web research for fact verification
• Pattern recognition across multiple files
• Complex decision-making for criticality levels
• Multi-step validation orchestration

docs-fixer (Sophisticated analysis):

model: sonnet

Reasoning:

• Re-validates findings to detect false positives
• Distinguishes objective errors from subjective improvements
• Assesses confidence levels (HIGH/MEDIUM/FALSE_POSITIVE)
• Complex decision-making for fix safety
• Trust model analysis (when to trust checker)

docs-tutorial-checker (Pedagogical analysis):

model: sonnet

Reasoning:

• Evaluates narrative flow and learning progression
• Assesses hands-on element quality
• Analyzes visual completeness
• Determines tutorial type compliance
• Sophisticated quality judgment

Haiku Examples

docs-link-general-checker (Straightforward validation):

model: haiku

Reasoning:

• Pattern matching to extract URLs
• Sequential URL validation via requests
• File existence checks for internal references
• Cache management (read/write YAML, compare dates)
• Simple status reporting (working/broken/redirected)
• No complex reasoning required

docs-file-manager (File operations):

model: haiku

Reasoning:

• Straightforward file operations (move, rename, delete)
• Simple path manipulation
• Git history preservation (scripted commands)
• No complex decision-making
• Deterministic outcomes

Documenting Model Selection

Model Selection Justification Pattern

Include in agent documentation to explain model choice:

For Sonnet Agents:

**Model Selection Justification**: This agent uses `model: sonnet` because it requires:

- [Reasoning capability 1 - e.g., "Advanced reasoning to analyze technical claims"]
- [Reasoning capability 2 - e.g., "Deep web research to verify facts"]
- [Reasoning capability 3 - e.g., "Pattern recognition across multiple files"]
- [Decision-making type - e.g., "Complex decision-making for criticality levels"]
- [Orchestration need - e.g., "Multi-step validation workflow orchestration"]

For Haiku Agents:

**Model Selection Justification**: This agent uses `model: haiku` because it performs straightforward tasks:

- [Simple task 1 - e.g., "Pattern matching to extract URLs"]
- [Simple task 2 - e.g., "Sequential URL validation via web requests"]
- [Simple task 3 - e.g., "File existence checks"]
- [Simple task 4 - e.g., "Cache management (read/write/compare)"]
- [Simple task 5 - e.g., "Simple status reporting"]
- No complex reasoning or content generation required

Placement in Agent Files

Add justification near the top of agent file, after agent description:

---
name: example-agent
description: Agent description here
model: sonnet
---

# Agent Name

**Model Selection Justification**: [justification here]

[Rest of agent documentation]

Cost and Performance Considerations

Sonnet Trade-offs

Costs:

• Higher per-token cost (~10x haiku)
• Slower response time
• More resource-intensive

Benefits:

• Higher quality reasoning
• Better context understanding
• More accurate decisions
• Handles ambiguity well

Use when: Quality and accuracy more important than cost/speed

Haiku Trade-offs

Benefits:

• Lower per-token cost (~10x cheaper)
• Faster response time
• Efficient for high-volume tasks

Limitations:

• Less sophisticated reasoning
• May struggle with ambiguity
• Better for deterministic tasks

Use when: Cost and speed more important than complex reasoning

Decision Checklist

Before selecting a model, ask:

1. Does the task require judgment calls?

   • Yes → Sonnet
   • No → Haiku

2. Are there multiple valid interpretations?

   • Yes → Sonnet
   • No → Haiku

3. Does it need deep analysis of context?

   • Yes → Sonnet
   • No → Haiku

4. Will it make complex decisions?

   • Yes → Sonnet
   • No → Haiku

5. Is it high-volume, low-complexity?

   • Yes → Haiku
   • No → Sonnet

6. Does cost matter more than quality?

   • Yes → Haiku
   • No → Sonnet

Common Mistakes

❌ Using Sonnet for Simple Tasks:

# Overkill - use haiku
model: sonnet # Just checking if files exist

❌ Using Haiku for Complex Analysis:

# Insufficient - use sonnet
model: haiku # Analyzing code quality and architecture

✅ Match Model to Task Complexity:

# Simple pattern matching
model: haiku

# Complex reasoning
model: sonnet

Key Takeaways

• Sonnet = Complex reasoning, sophisticated analysis, multi-step orchestration
• Haiku = Simple tasks, pattern matching, straightforward validation
• Document rationale = Include model selection justification in agent files
• Consider trade-offs = Balance cost/speed vs quality/capability
• Match complexity = Use appropriate model for task requirements
• When in doubt = Choose sonnet for quality, haiku for speed/cost

Proper model selection ensures optimal performance, cost-effectiveness, and task completion quality.