pluck-mcp 0.3.0

Quickstart • Why Pluck? • MCP Tools • CLI • Benchmarks

pluck is a local Rust daemon that replaces cat and grep as the default way AI agents read and search code. It exposes symbol-aware code reading and search to agents over the Model Context Protocol (MCP). Smart outlines cut eligible code-read tokens by 84-88 %, CI logs compress by 71 %, and warm search stays sub-millisecond — with a --raw fallback on every tool so the agent never loses capability by defaulting to pluck.

Without pluck:  ls → grep → cat file1 → cat file2 → cat file3 → ...
With pluck:     pluck.plan "fix auth-token expiry"  → 3-5 next-call recommendations
                pluck.search "auth flow"            → ranked chunks, BM25 + semantic
                pluck.peek validate_token           → signature + callees only
                pluck.symbol validate_token         → just that function's body
                pluck.impact validate_token         → every caller, depth-capped
                pluck.deps src/auth/login.ts        → forward/reverse import graph
                pluck.digest < cargo-build.log      → 71 % shorter, errors intact

Quickstart

Pluck is designed to be the default retrieval tool for your AI coding agents.

1. Install Pluck

# Daemon + standalone CLI from crates.io
cargo install pluck-mcp pluck-cli

# Or via Homebrew tap
brew tap hunhee98/pluck && brew install pluck

2. Add to your Agent

Claude Code

pluck init --target claude
pluck init --target claude --mode aggressive  # also blocks Bash cat/rg retrieval

(Alternatively, you can manually enable it via /plugin marketplace add hunhee98/pluck)

Codex

pluck init --target codex

Cursor

pluck init --target cursor

Why pluck?

When AI agents use standard cat and grep to explore a codebase, they waste massive amounts of context window tokens. Re-reading the same file chunk, scrolling past unrelated functions, and re-paying tokens for identical imports on every read adds up to thousands of wasted tokens per session.

pluck solves this by providing an agent-facing layer for code search. Its core principle: every retrieval call an agent makes should default to pluck. Bash is only the fallback when pluck legitimately can't help (e.g., binary files, paths outside the repo).

• Smart Outline (pluck.read): Instead of dumping a 1,000-line file, it returns a token-efficient outline of signatures with tiny helper bodies inline. The agent can then fetch only the larger function bodies it needs.
• Session Dedup: If an agent searches for "auth" and later searches for "token", any overlapping code chunks are replaced with a 1-token placeholder ([already-shown: ...]). The bytes are already in the agent's context; repeating them is pure waste.
• Lossless Default: Stripping comments or dropping types hurts the agent's decision-making. pluck keeps the original bytes intact and makes lossy modes strictly opt-in.
• 100% Capability Guarantee: Every pluck tool has a --raw fallback that behaves exactly like cat or grep byte-for-byte.

How it works

pluck chunks files at the Abstract Syntax Tree (AST) level using Tree-sitter. When an agent queries, pluck ranks these chunks using a hybrid of keyword matching (BM25F over symbol/signature/content) and semantic similarity (a static model2vec-style lookup, potion-code-16M, ~60 MB on disk — no transformer inference at runtime). Search expands natural-language BM25 queries with embedding-nearest terms from the indexed repo, then runs a two-stage cascade: BM25F first widens the candidate pool, embeddings rerank that pool, and a smaller semantic-rescue pass catches concept queries with weak lexical overlap. The RRF blend is picked continuously from the query embedding against natural-language and code centroids, so agents can search by concept ("payment flow") without losing precision on exact symbols.

Session dedup in action

MCP Tools

Agents call specific tools depending on what they need. Bash is the fallback, not the default.

Standalone CLI (no agent)

You can also use pluck directly in your terminal:

pluck index .
pluck search "auth flow" --repo .
pluck read src/auth/login.ts        # smart outline
pluck read src/auth/login.ts --raw  # byte-equivalent cat

Performance & Token Savings

Every number on this page cites a frozen baseline row or a measured scenario. No projected / aspirational percentages.

Gated engine metrics

These are the invariants in benchmarks/baseline.json. Every commit that touches engine-core runs scripts/regression-gate.py and the gate fails the build if any of them drift past tolerance.

Eligible read-token savings

pluck.read outline mode is where pluck stops agents from paying the cat tax: instead of dumping every line, it returns the file's symbol map, inlines tiny helper bodies, and lets the agent fetch larger bodies on demand.

Tiny files and raw reads are control cases: they are expected to show little or no savings because byte-exact fallback is the point.

Measured single-scenario token reduction

fix-auth-token-expiry: same JIRA-style task, bash workflow (rg -l + several cats) vs pluck workflow (search + read + symbol). Both runners arrive at the same fix:

Broader LLM-in-the-loop measurements across fix / refactor / explore / search / review scenarios are roadmapped as v0.5.0 work. We'll publish those numbers when they exist, not before.

Feature Comparison

Roadmap

• v0.2.0 — shipped: First crates.io publish, MCP tools, session dedup, smart outline, and expanded surface — digest, impact, deps, plan.
• v0.3.0 — shipped: Natural-language recall — 100-query suite across tokio / django / next.js, query expansion, two-stage cascade, continuous hybrid weighting, NDCG@10 measurement, and symbol/path component ranking.
• v0.4.0 — next: Language coverage — Java, C / C++, Kotlin, Ruby, PHP, Swift.
• v0.5.0: Adoption-rate counter, tool-description A/B harness, LLM-in-loop bench, Aider / OpenHands / Cursor hooks.

License

MIT - See LICENSE for details.