Oss Search MCP Server

oss-search

Fast local + federated OSS code search and repo discovery, built for AI agents (MCP) with a CLI twin.

Not recreating the wheel is a superpower. oss-search answers two questions for an agent:

1. Which library already solves this? — multi-signal repo ranking (dependents, centrality, maintenance, security posture), not just star count.
2. Show me real code that does this — sub-50ms regex search over a local hot-set corpus, federated with live backends (GitHub code search, grep.app, Sourcegraph) for the long tail.

Highlights

• 7 MCP tools (oss_search_repos, oss_search_code, oss_repo_profile, oss_repo_tree, oss_fetch_file, oss_fetch_docs, oss_guide) over stdio, plus a byte-identical CLI.
• Local trigram index: pure-Rust positional-trigram engine. Measured p50 ≈ 34ms over a 13,408-file / 100-repo hot-set; incremental reindex touches only changed blobs.
• Hybrid semantic layer: tree-sitter function-level chunking (Rust/Python/JS/TS/Go/C), local embeddings (fastembed, BGE-small), RRF fusion with lexical-first routing — identifier queries never pay model latency.
• Repo discovery ranking: dependents count, dependency-graph PageRank (CSR power iteration), OpenSSF-style maintenance/security signals, awesome-list membership, archived/stale gates — with per-signal contributions inspectable in every result.
• Corpus pipeline: blobless depth-1 clones → BLAKE3 content-addressed zstd store → 3-tier dedup (content / token / MinHash-LSH with exact Jaccard verification) → SPDX license detection.
• Strict agent-facing contract: structured filters, typed pre-execution errors (unknown_field / regex_error / not_indexable) that echo the input and name the correction, declared total/hasMore/partial, ~25KB response cap, never silent degradation.
• Security posture: RE2-class regex only (linear time, ReDoS-immune), file admission gates, output escaping (ANSI/control chars, bidi overrides) — all verified by test.

Install

Two front doors: oss-mcp (MCP server) and oss-cli (CLI twin). Three ways to get them:

1. npm — an oss-search shim that downloads the platform-matched prebuilt binary on first run and caches it under ~/.cache/oss-search/bin/ (override with OSS_SEARCH_CACHE_DIR):

npx -y oss-search --version

2. cargo install (requires a Rust toolchain):

cargo install oss-mcp oss-cli
# or the unreleased tip of main:
cargo install --git https://github.com/sblattj/oss-search oss-mcp
cargo install --git https://github.com/sblattj/oss-search oss-cli

Binaries land in ~/.cargo/bin/.

3. Prebuilt binaries — every release publishes oss-search-<version>-<target>.tar.gz plus checksums.txt (sha256) at https://github.com/sblattj/oss-search/releases/latest, for targets aarch64-apple-darwin, x86_64-apple-darwin, aarch64-unknown-linux-gnu, x86_64-unknown-linux-gnu:

curl -fsSL https://github.com/sblattj/oss-search/releases/latest/download/oss-search-0.3.2-aarch64-apple-darwin.tar.gz | tar xz

From a checkout instead:

cargo build --release
# binaries: target/release/oss-mcp  target/release/oss-cli

Quickstart (CLI)

oss-cli mirrors the 7-tool surface one-to-one (offline stub engine by default; --live switches to the real backends):

# Probe-writing and query-syntax playbook — offline, zero setup
oss-cli guide

# Repo discovery — which wheel exists?
oss-cli search-repos --query "express" --limit 5

# Code search by distinctive idioms (federated; GITHUB_TOKEN unlocks the github backend)
GITHUB_TOKEN=... oss-cli --live search-code --probe "retry_with_backoff" --limit 3

All commands emit the same structured JSON envelope (results, total, has_more, partial, backend_status) that the MCP tools return.

Quickstart (MCP)

oss-mcp speaks MCP over stdio. Invocation safety: --help / --version print and exit 0 without ever starting the server; unknown arguments exit 2 with usage instead of silently serving a stub; with no arguments it serves until stdin closes.

Claude Code — .mcp.json at the project root (use the absolute path your install produced, or the npx form):

{
  "mcpServers": {
    "oss-search": {
      "command": "/Users/YOU/.cargo/bin/oss-mcp",
      "args": ["--live"],
      "env": { "GITHUB_TOKEN": "ghp_..." }
    }
  }
}

npx form (no absolute path needed):

{
  "mcpServers": {
    "oss-search": {
      "command": "npx",
      "args": ["-y", "oss-search", "--live"],
      "env": { "GITHUB_TOKEN": "ghp_..." }
    }
  }
}

Claude Desktop — claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json; ~ is not expanded inside the JSON — use the absolute path):

{
  "mcpServers": {
    "oss-search": {
      "command": "/Users/YOU/.cargo/bin/oss-mcp",
      "args": ["--live"],
      "env": { "GITHUB_TOKEN": "ghp_..." }
    }
  }
}

opencode — opencode.json at the project root:

{
  "mcp": {
    "oss-search": {
      "type": "local",
      "command": ["oss-mcp", "--live"],
      "environment": { "GITHUB_TOKEN": "ghp_..." },
      "enabled": true
    }
  }
}

--live enables the remote backends (GitHub REST code and repository search, grep.app via its MCP endpoint, Sourcegraph, deps.dev, ecosyste.ms, npms.io); without it oss-mcp serves an offline stub. oss_search_repos draws candidates from npms.io (npm packages) and GitHub repository search (any language), dedupes them by owner/name, and scores both with the same per-signal model; a GitHub-only repo has no dependents signal, so it is scored on stars, recency, and license. Without GITHUB_TOKEN repository search is limited to 10 requests/min. Sourcegraph answers anonymously; set SOURCEGRAPH_TOKEN for higher rate limits. oss-mcp --help prints the full invocation contract.

Query language

retry repo:tokio-rs/tokio lang:rust path:src/ case:yes scope:def in:hotset type:regex

Structured JSON fields are canonical (arrays = OR, across fields = AND, - prefixes = excludes). Unknown fields are rejected loudly with the known-field list — never silently dropped.

Verification

The repo ships its own evidence: data/e2e/E2E-REPORT.md (9/9 gate through the release binaries), golden-set eval (data/e2e/eval/EVAL.md), and the hot-set latency table (data/e2e/hotset/LATENCY.md).

cargo test --workspace   # 432 tests

Workspace layout

License

MIT