tool-design
Use when designing agent tools, creating tool descriptions, implementing MCP tools, or asking about "tool design", "agent tools", "tool descriptions", "MCP", "function calling", "tool consolidation"
What this skill does
# Tool Design for Agents
Tools define the contract between deterministic systems and non-deterministic agents. Poor tool design creates failure modes that no amount of prompt engineering can fix.
## The Consolidation Principle
If a human engineer cannot definitively say which tool should be used, an agent cannot do better.
**Instead of**: `list_users`, `list_events`, `create_event`
**Use**: `schedule_event` (finds availability and schedules)
## Tool Description Structure
Answer four questions:
1. **What** does the tool do?
2. **When** should it be used?
3. **What inputs** does it accept?
4. **What** does it return?
## Well-Designed Tool Example
```python
def get_customer(customer_id: str, format: str = "concise"):
"""
Retrieve customer information by ID.
Use when:
- User asks about specific customer details
- Need customer context for decision-making
- Verifying customer identity
Args:
customer_id: Format "CUST-######" (e.g., "CUST-000001")
format: "concise" for key fields, "detailed" for complete record
Returns:
Customer object with requested fields
Errors:
NOT_FOUND: Customer ID not found
INVALID_FORMAT: ID must match CUST-###### pattern
"""
```
## Poor Tool Design (Anti-pattern)
```python
def search(query):
"""Search the database."""
pass
```
**Problems**: Vague name, missing parameters, no return description, no usage context, no error handling.
## Architectural Reduction
Production evidence shows: fewer, primitive tools can outperform sophisticated multi-tool architectures.
**File System Agent Pattern**: Provide direct file system access instead of custom tools. Agent uses grep, cat, find to explore. Works because file systems are well-understood abstractions.
**When reduction works**:
- Data layer well-documented
- Model has sufficient reasoning
- Specialized tools were constraining
- Spending more time maintaining scaffolding than improving
## MCP Tool Naming
Always use fully qualified names:
```python
# Correct
"Use the BigQuery:bigquery_schema tool..."
# Incorrect (may fail)
"Use the bigquery_schema tool..."
```
## Response Format Optimization
```python
format: str = "concise" # "concise" | "detailed"
```
Let agents control verbosity. Concise for confirmations, detailed when full context needed.
## Error Message Design
Design for agent recovery:
```python
{
"error": "NOT_FOUND",
"message": "Customer CUST-000001 not found",
"suggestion": "Verify customer ID format (CUST-######)"
}
```
## Tool Collection Guidelines
- 10-20 tools for most applications
- Use namespacing for larger collections
- Ensure each tool has unambiguous purpose
- Test with actual agent interactions
## Anti-Patterns
- **Vague descriptions**: "Search the database"
- **Cryptic parameters**: `x`, `val`, `param1`
- **Missing error handling**: Generic errors
- **Inconsistent naming**: `id` vs `identifier` vs `customer_id`
## Best Practices
1. Write descriptions answering what, when, returns
2. Use consolidation to reduce ambiguity
3. Implement response format options
4. Design error messages for recovery
5. Establish consistent naming conventions
6. Test with actual agent interactions
7. Question if tools enable or constrain reasoning
8. Build minimal architectures for model improvements
Related in Design
contribute
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mcp
IncludedModel Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.
react-native-skia
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plaid
IncludedProduct Led AI Development — guides founders from idea to launched product. Six capabilities: Idea (discover a product idea), Validate (pressure-test the idea against fatal flaws, problem reality, competition, and 2-week MVP feasibility), Plan (vision intake + document generation), Design (translate image references into a design.md spec), Launch (go-to-market strategy), and Build (roadmap execution). Use when someone says "PLAID", "plaid idea", "help me find an idea", "product idea", "idea from my business", "idea from my expertise", "plaid validate", "validate my idea", "pressure-test", "is this idea good", "find fatal flaws", "validate the problem", "plan a product", "define my vision", "generate a PRD", "product strategy", "plaid design", "design from image", "translate image to design", "create design.md", "extract design tokens", "plaid launch", "go-to-market", "launch plan", "GTM strategy", "launch playbook", "plaid build", "build the app", "start building", or "execute the roadmap".
nextjs-framer-motion-animations
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