example-call-chain

name	example-call-chain
description	Call-chain tracing skill template. Guides creation of project-specific call-chain skills for tracing API data flow, verifying type matching, and checking endpoint correctness.
model_tier	L1
skill_tier	functional
version	1.0.0
status	active

牵一发而动全身。 ——龚自珍《自春徂秋偶有所触》 改一行代码之前先知道谁在调用它。这不是顾虑，是常识。

Call-Chain Tracing Skill Template

Positioning: Functional tier skill — provides structured call-chain tracing methodology for verifying data flow correctness. Orchestrated by delegation (planning) and skill-builder-guide (meta).

Trigger Conditions

• Tracing API call chains, data flow, request lifecycle
• "How does data flow from X to Y"
• "What calls what in this endpoint"
• Verifying type matching across layers
• Creating project-specific call-chain skills

Related Skills

• Dev Standards — layer conventions and naming
• Code Map — file locations [L0]
• Change Model — call-chain check integration

---

1. Tracing Method

Step 1: Identify entry point
  ├─ API endpoint / event handler / scheduled task / message consumer
  └─ Record: input types, validation rules

Step 2: Trace through layers
  ├─ Entry layer → Business layer → Data layer → External calls
  └─ Record at each layer: method name, parameter types, return type

Step 3: Verify final call
  ├─ SQL query / external API call / message publish / cache write
  └─ Check: parameters correctly assembled, types match

Step 4: Error path check
  ├─ Exceptions caught at each layer?
  └─ Error response includes correct status code?

2. Call-Chain Template

## {Endpoint Name} Call Chain

{Caller}
  │ {HTTP method} {path}
  ▼
{Controller}.{method}({param}: {type})
  │ → calls {Service}.{method}({param}: {type})
  ▼
{Service}.{method}({param}: {type})
  │ → business logic: {summary}
  │ → calls {Repository}.{method}({query})
  ▼
{Repository}.{method}({query})
  │ → {SQL / external API / message}
  ▼
{Database / External Service}

3. Type Matching Checklist

#	Layer Transition	Check	Status
1	Request → Controller	Param types match DTO	✅/❌
2	Controller → Service	Service param = DTO or derived type	✅/❌
3	Service → Repository	Query params match Prisma/SQL types	✅/❌
4	Service → External	API contract types match	✅/❌
5	Service → Response	Return type matches API schema	✅/❌

4. Customization

When generating a project-specific call-chain skill, map the project's actual layer names to the tracing template. Include project-specific external API call signatures, error handling patterns, and one worked example of a real endpoint's full chain.

Architecture-specific tracing patterns (CLI, event-driven, frontend, layered backend): references/tracing-patterns.md.

Handoff

After completing this skill, recommend the next skill based on output characteristics:

Condition	Recommend
New change requirement found	{project}-change-model

5. Model Tier

L1 — Sonnet / functional tier: Requires code-level tracing and type-compatibility reasoning. File lookups delegated to L0 — Haiku.