memtrace-impact

name

memtrace-impact

description

Compute the blast radius of modifying a symbol through transitive graph impact. Use when the user asks about blast radius, impact, what breaks, risk, upstream callers, downstream dependencies, or consequences of modifying a symbol, before or during source-code changes. Do not use Grep or manual reference search; Memtrace computes transitive graph impact. For a full risk-rated plan covering a multi-part change, use memtrace-change-impact-analysis.

Overview

Compute the blast radius of changing a specific symbol. Traces upstream (what depends on this) and downstream (what this depends on) through the knowledge graph to quantify risk before making modifications.

Quick Reference

Tool	Purpose
get_impact	Blast radius from a symbol name (target)
detect_changes	Scope symbols affected by a diff/patch

Parameter types: MCP parameters are strictly typed. Numbers (depth, limit, etc.) must be JSON numbers — not strings.

Required parameters — get_impact

Parameter	Required	Default	Notes
repo_id	yes	—
target	yes	—	Symbol name (e.g. "validateToken") — not symbol_id
direction	no	"both"	"upstream" | "downstream" | "both"
depth	no	5	BFS depth (max 15)
as_of	no	now	ISO-8601 for time-travel

{ "repo_id": "memdb", "target": "validateToken", "direction": "both", "depth": 5 }

Full parameter spec for every Memtrace tool: references/mcp-parameters.md (bundled at the memtrace-skills plugin root).

Steps

1. Identify the symbol name

If you don't know the exact name:

• find_symbol(name="...") for exact identifiers
• find_code(query="...") for natural-language queries

Use the returned name (and optional file_path hint) — graph tools resolve by name, not internal IDs.

2. Run impact analysis

{
  "repo_id": "memdb",
  "target": "validateToken",
  "direction": "upstream",
  "depth": 5
}

3. Interpret the risk rating

Risk	Meaning	Action
Low	Few dependents, leaf node	Safe to modify; minimal testing needed
Medium	Moderate dependents	Test direct callers; review interface contracts
High	Many dependents across modules	Coordinate changes; comprehensive test coverage
Critical	Core infrastructure, many transitive dependents	Plan migration strategy; backward-compatible changes

4. For diff-based analysis

When you have an actual code diff, use detect_changes:

{ "repo_id": "memdb", "diff": "<unified git diff text>" }

Or pass changed_files: ["path/a.rs", "path/b.ts"] when no diff text is available.

Decision Points

Situation	Action
Changing a single function	get_impact with direction: "both"
Reviewing a PR or diff	detect_changes with the diff content
Renaming/removing a public API	get_impact with direction: "upstream", higher depth
Refactoring internals	get_impact with direction: "downstream"

Output

get_impact returns the blast radius for the target symbol:

Field	Example / meaning
Risk rating	High — one of Low / Medium / High / Critical (interpret via step 3)
Upstream	Transitive dependents (callers/importers) within depth hops — what breaks if the target changes
Downstream	Transitive dependencies — what the target relies on

detect_changes returns the set of symbols affected by the supplied diff / changed_files, plus the affected processes (execution flows).

Common Mistakes

Mistake	Reality
Passing symbol_id or name	Required param is target
Omitting repo_id	Both repo_id and target are required
Defaulting depth to 3	API default is 5