Call Trace

Call Trace: map the full call chain in both directions

You are gathering deep context around a target piece of code before it's changed or assessed — tracing every caller above it (upstream) and every callee below it (downstream). Your job is to build a complete picture of how the code is reached and what it touches, then stop. This is a context-gathering skill: you read and map, you do not edit.

The failure mode this skill exists to prevent is shallow tracing — reading a 20-line window around each call site and missing the side effects, early returns, and branches that live in the rest of the method. Read whole method bodies, always; partial windows produce confident-but-wrong analysis.

When to use this skill

• "Get a full / complete understanding" of how something works, or any close variant.
• Tracing callers, assessing blast radius, or understanding how a method is used.
• Before changing shared or foundational code where the impact isn't obvious.
• Working through PR review feedback — trace each review item independently.

When NOT to use this skill

• You only need a single definition or a quick lookup — just Read/Grep it; a full bidirectional trace is overkill.
• You're about to make a small, well-understood, local change — don't manufacture a trace for it.
• You need to edit code — this skill only gathers context; move to the change once the trace is done.

Upward trace (callers)

1. Find callers. Grep for every call site of the target method/function across the repo.
2. Read whole bodies. For each caller, Read the entire containing method — signature to end. Never just a window around the call site.
3. Recurse upward. Identify what calls that method and repeat, building the chain toward the entry points.
4. Stop at an entry point or dead end:

• A request/route handler — the app's inbound edge (HTTP, RPC, GraphQL resolver).
• A background or scheduled entry point (job runner, message/queue consumer, cron/timer task, worker loop).
• A CLI command, or the program's main/startup entry point.
• A test.
• A public API surface with no callers inside this repo.
• A method invoked only via dependency-injection/reflection/registration with no static callers — note it and stop.

Downward trace (callees)

1. List callees. From the target, identify every non-trivial method/function it calls. Skip standard-library and noise calls (collection/string helpers, logging, simple getters).
2. Read whole bodies. Read the full body of each callee.
3. Recurse downward into their callees until a dead end: the data-access/persistence layer, an external client (HTTP/SDK/queue publish), third-party or standard-library code, or a pure helper with no further branching.

Rules

What to do

• Read whole method bodies — always. Signature to end. The side effects and branches that matter are rarely next to the call site.
• Parallelize by depth. Issue all Read calls at the same depth in a single batched tool block; never serialize reads that don't depend on each other.
• Stay inside the current repo by default. If a caller or callee lives in another service/package, note it by name and stop there. Cross a repo/service boundary only when the user explicitly asks.

What NOT to do

• NEVER read narrow windows around a call site — it is the cardinal sin here; it produces shallow analysis and missed side effects.
• Don't chase trivial callees (standard-library/collection helpers, logging) — they add noise, not understanding.
• Don't delegate to subagents by default. Agent summaries sacrifice the raw-code fidelity this skill exists to preserve. Fan out only when (a) the call graph is very wide and most branches are clearly irrelevant, or (b) the user opted into a cross-repo trace.

Format discipline

• Token usage and speed are not concerns here — accuracy and full context are the only priorities.
• When the trace is done, summarize the chain in both directions (entry points → target → leaves) and call out the side effects you found. Then stop — do not start editing.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: SamuelBostic29
• Source: SamuelBostic29/claude-skills
• License: MIT

Install and usage instructions live in the source repository linked above.