# Gcf Rust

> GCF Rust implementation. 100% LLM comprehension on every frontier model. 50-92% fewer tokens than JSON. 43B+ round-trips verified. Zero dependencies.

- **Type:** MCP server
- **Install:** `agentstack add mcp-blackwell-systems-gcf-rust`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [blackwell-systems](https://agentstack.voostack.com/s/blackwell-systems)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [blackwell-systems](https://github.com/blackwell-systems)
- **Source:** https://github.com/blackwell-systems/gcf-rust
- **Website:** https://www.gcformat.com

## Install

```sh
agentstack add mcp-blackwell-systems-gcf-rust
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# gcf-rust

Rust implementation of [GCF](https://gcformat.com/) -- the most token-efficient wire format for LLMs. A drop-in alternative to JSON and TOON for any structured data.

**100% comprehension on every frontier model tested. 29% fewer tokens than TOON, 56% fewer than JSON across 16 datasets. 91.2% on structurally complex code graphs (vs TOON 68.8%, JSON 54.1%). 2,400+ LLM evaluations. Zero training.**

Docs: [gcformat.com](https://gcformat.com/) | [Playground](https://gcformat.com/playground.html) | [GCF vs TOON](https://gcformat.com/guide/vs-toon.html)

## Install

```toml
[dependencies]
gcf = "0.1"
```

Zero-copy where possible. Minimal dependencies (serde, serde_json). Don't want to change code? Use the [MCP proxy](https://github.com/blackwell-systems/gcf-proxy) for zero-code adoption.

## Quick Start

```rust
use gcf::encode_generic;
use serde_json::json;

let data = json!({
    "employees": [
        {"id": 1, "name": "Alice", "department": "Engineering", "salary": 95000},
        {"id": 2, "name": "Bob", "department": "Sales", "salary": 72000},
    ],
});
let output = encode_generic(&data);
```

Output:
```
## employees [2]{department,id,name,salary}
Engineering|1|Alice|95000
Sales|2|Bob|72000
```

Works on any `serde_json::Value`. One header declares field names, rows are positional values.

## Graph Profile

For code graph data with symbols, edges, and distance groups:

```rust
use gcf::{Payload, Symbol, Edge, encode};

let p = Payload {
    tool: "context_for_task".into(), token_budget: 5000, tokens_used: 1847,
    symbols: vec![
        Symbol { qualified_name: "pkg.Auth".into(), kind: "function".into(), score: 0.78, provenance: "lsp".into(), distance: 0, ..Default::default() },
        Symbol { qualified_name: "pkg.Server".into(), kind: "function".into(), score: 0.54, provenance: "lsp".into(), distance: 1, ..Default::default() },
    ],
    edges: vec![Edge { source: "pkg.Server".into(), target: "pkg.Auth".into(), edge_type: "calls".into(), ..Default::default() }],
    ..Default::default()
};
let output = encode(&p);
```

Output:
```
GCF tool=context_for_task budget=5000 tokens=1847 symbols=2 edges=1
## targets
@0 fn pkg.Auth 0.78 lsp
## related
@1 fn pkg.Server 0.54 lsp
## edges [1]
@0 String` | Encode a graph payload to GCF text |
| `encode_generic(data: &Value) -> String` | Encode any JSON value to GCF tabular format |
| `decode(input: &str) -> Result` | Parse GCF text back to a Payload |
| `encode_with_session(p: &Payload, s: &Session) -> String` | Encode with session deduplication |
| `encode_delta(d: &DeltaPayload) -> String` | Encode a delta (added/removed only) |
| `Session::new() -> Session` | Create a new session tracker (thread-safe via Mutex) |

## Types

| Type | Purpose |
|------|---------|
| `Payload` | Full GCF payload: tool, budget, symbols, edges, pack root |
| `Symbol` | Graph node: qualified name, kind, score, provenance, distance |
| `Edge` | Directed relationship: source, target, edge type |
| `DeltaPayload` | Diff between two packs: added/removed symbols and edges |
| `Components` | Score breakdown: blast_radius, confidence, recency, distance |
| `Session` | Thread-safe tracker for multi-call deduplication |
| `DecodeError` | Enum of decode failure modes |

## Benchmarks

2,400+ LLM evaluations across 10 models, 3 providers, and 51 independent test runs.

| | GCF | TOON | JSON |
|---|---|---|---|
| **Comprehension** (23 runs, 10 models) | **91.2%** | 68.8% | 54.1% |
| **Generation** (28 runs, 9 models) | **5/5** | 1.0/5 | 5.0/5 |
| **Input tokens** (500 symbols) | **11,090** | 16,378 | 53,341 |
| **Output tokens** (100 symbols) | **5,976** | 8,937 | 16,121 |

GCF wins 15/16 datasets on the expanded [token efficiency benchmark](https://github.com/blackwell-systems/toon/tree/gcf-comparison). Full results: [gcformat.com/guide/benchmarks](https://gcformat.com/guide/benchmarks.html)

## Implementations

| Language | Package | Repository |
|----------|---------|-----------|
| Go | `go get github.com/blackwell-systems/gcf-go` | [gcf-go](https://github.com/blackwell-systems/gcf-go) |
| TypeScript | `npm install @blackwell-systems/gcf` | [gcf-typescript](https://github.com/blackwell-systems/gcf-typescript) |
| Python | `pip install gcf-python` | [gcf-python](https://github.com/blackwell-systems/gcf-python) |
| Rust | `cargo add gcf` | [gcf-rust](https://github.com/blackwell-systems/gcf-rust) |
| Swift | Swift Package Manager | [gcf-swift](https://github.com/blackwell-systems/gcf-swift) |
| Kotlin | JitPack | [gcf-kotlin](https://github.com/blackwell-systems/gcf-kotlin) |
| MCP Proxy | `pip install gcf-proxy` | [gcf-proxy](https://github.com/blackwell-systems/gcf-proxy) (bidirectional, session dedup, HTTP frontend) |
| Claude Code Plugin | `/plugin install` | [gcf-claude-plugin](https://github.com/blackwell-systems/gcf-claude-plugin) (one-command install, session stats hook) |
| Codex Plugin | `codex plugin add` | [gcf-codex-plugin](https://github.com/blackwell-systems/gcf-codex-plugin) (one-command install, session stats hook) |
| VS Code | `ext install blackwell-systems.gcf-vscode` | [gcf-vscode](https://marketplace.visualstudio.com/items?itemName=blackwell-systems.gcf-vscode) (syntax highlighting) |
| n8n | `npm install n8n-nodes-gcf` | [gcf-n8n-nodes](https://github.com/blackwell-systems/gcf-n8n-nodes) (workflow encode/decode) |
| Tree-sitter | `npm install tree-sitter-gcf` | [tree-sitter-gcf](https://github.com/blackwell-systems/tree-sitter-gcf) |

**Minimal dependencies. Permanently.** Rust implementation depends only on serde and serde_json for JSON interop. Five other implementations (Go, TypeScript, Python, Swift, Kotlin) have zero runtime dependencies. No unnecessary transitive dependencies. No supply chain risk. This is a permanent commitment: GCF will never take on external runtime dependencies beyond what the language ecosystem requires for JSON handling. MIT licensed. All implementations support both generic profile (`encode_generic`) and graph profile (`encode`). CLI included in all 6 languages.

**Specification:** [SPEC v3.2 Stable](https://github.com/blackwell-systems/gcf/blob/main/SPEC.md) with 174 conformance fixtures, 43,000,000,000+ lossless round-trips verified across 5 formats and 6 languages. All implementations at v2.2.1+ (Go v1.3.1). Cross-language 6x6 matrix verified.

## License

MIT - [Dayna Blackwell](https://github.com/blackwell-systems)

## Source & license

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

- **Author:** [blackwell-systems](https://github.com/blackwell-systems)
- **Source:** [blackwell-systems/gcf-rust](https://github.com/blackwell-systems/gcf-rust)
- **License:** MIT
- **Homepage:** https://www.gcformat.com

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

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/mcp-blackwell-systems-gcf-rust
- Seller: https://agentstack.voostack.com/s/blackwell-systems
- Browse the marketplace: https://agentstack.voostack.com/browse

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