Memorylens MCP README
The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Memorylens MCP listing page.
MemoryLens MCP
On-demand .NET memory profiling with concrete, AI-actionable code fix suggestions — no profiler to install.
Hosted deployment
A hosted deployment is available on Fronteir AI.
Quick Start
npx (any MCP client)
The npm package ships no server code — it is a launcher that installs the MemoryLens.Mcp .NET
global tool at a matching version and execs it, so the .NET 10 SDK must be on PATH.
Subsequent starts skip the install entirely and work offline.
VS Code / Visual Studio (via dnx)
Add to your MCP settings (.vscode/mcp.json or VS settings):
Claude Code Plugin
.NET Global Tool
Docker
Profiling from a container needs ptrace and the host PID namespace, and on
Docker Desktop that namespace is the Linux VM rather than your desktop — see
docs/docker.md before choosing this route.
-v /tmp:/tmp is what makes list_processes return anything — the runtime's
diagnostic sockets live in the temp directory — and it is also what keeps
snapshots alive after --rm, since they are written to
/tmp/memorylens-snapshots inside the container. -v "$PWD:/workspace" is only
so .memorylens.json is picked up; nothing is written there.
Prerequisites
- .NET 10 SDK, 10.0.4xx feature band (pinned in
global.json)
Running a filtered subset of the tests, e.g. dotnet test --filter <name>, will exit with code 9
and print error: 1, failed: 0. That's the test project's discovery-collapse guard
(--minimum-expected-tests) firing because the filter left fewer tests than expected — it is
not a test failure, and a full dotnet test run is unaffected.
How Collection Works
MemoryLens collects heap data in-process over EventPipe, the .NET runtime's built-in diagnostics channel. There is no profiler to install, no download on first use, and no external tool on PATH.
snapshot attaches to a running .NET process by pid, induces a collection, and aggregates the heap into per-type counts and sizes. Snapshots are written as small JSON files under your temp directory and referenced by a short id.
On Linux and in containers, attaching to another process's diagnostic endpoint may require matching UID or SYS_PTRACE — see docs/docker.md.
Available MCP Tools
| Tool | Description |
|---|---|
list_processes | Lists running .NET processes available for profiling, discovered from their diagnostic IPC endpoints |
snapshot | Captures a single memory snapshot of a target process |
compare_snapshots | Captures two snapshots with configurable delay and compares them |
analyze | Runs the rule engine against a captured snapshot and returns findings |
get_rules | Lists all available analysis rules with their metadata |
Built-in Rules
| ID | Severity | Category | Description |
|---|---|---|---|
| ML001 | critical | leak | Event handler leak detected |
| ML002 | critical | leak | Static collection growing unbounded |
| ML003 | high | leak | Disposable object not disposed |
| ML004 | high | fragmentation | Large Object Heap fragmentation |
| ML005 | medium | retention | Object retained longer than expected |
| ML006 | medium | allocation | Excessive allocations in hot path |
| ML007 | medium | retention | Closure retaining unexpected references |
| ML008 | low | allocation | Array/list resizing without capacity hint |
| ML009 | low | pattern | Finalizer without Dispose pattern |
| ML010 | low | pattern | String interning opportunity |
Configuration
Create a .memorylens.json file in your project root to customize rule behavior:
Usage Examples
Single Snapshot
Capture a memory snapshot of a running process to inspect current memory state:
Claude will call snapshot with the target PID, then analyze the returned snapshot id and present findings ordered by severity.
Before/After Comparison
Detect memory growth by comparing two snapshots taken with a delay:
Claude will call compare_snapshots with a delaySeconds value (default 10 seconds) between the two captures, then analyze the diff to identify objects that grew between snapshots.