# Fastcontext Agent Tools

> MCP server and Codex skill for Microsoft FastContext repository exploration

- **Type:** MCP server
- **Install:** `agentstack add mcp-jakevin-fastcontext-agent-tools`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [Jakevin](https://agentstack.voostack.com/s/jakevin)
- **Installs:** 0
- **Category:** [Integrations](https://agentstack.voostack.com/c/integrations)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [Jakevin](https://github.com/Jakevin)
- **Source:** https://github.com/Jakevin/fastcontext-agent-tools

## Install

```sh
agentstack add mcp-jakevin-fastcontext-agent-tools
```

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

## About

# FastContext Agent Tools

MCP server and Codex skill for using Microsoft's FastContext as a read-only
repository exploration subagent.

FastContext answers one narrow question for a coding agent:

> Which files and line ranges should the main agent inspect before solving this task?

This repository provides the complete integration:

- `fastcontext-mcp`: a Python stdio MCP server that installs Microsoft FastContext as a pinned runtime dependency.
- `skills/fastcontext-explorer`: a Codex skill that teaches an agent when to delegate repository exploration.
- MCP setup guides in English, Traditional Chinese, and Japanese.

It does not bundle model weights, run inference, or modify repositories. The MCP
server runs the bundled `fastcontext.cli` module in the same Python environment
and returns candidate file-line citations for the main agent to verify.

## One-Line LLM Agent Install Prompt

Ask an LLM agent:

> Install FastContext Agent Tools from `https://github.com/Jakevin/fastcontext-agent-tools`; its package installation includes Microsoft FastContext. Configure `python -m fastcontext_mcp` as a stdio MCP server with `BASE_URL`, `MODEL`, `API_KEY`, and `FASTCONTEXT_ALLOWED_ROOTS`, then enable `skills/fastcontext-explorer`.

Direct install command for Codex-style local skills:

```bash
git clone https://github.com/Jakevin/fastcontext-agent-tools && cd fastcontext-agent-tools && python -m pip install -e . && mkdir -p "${CODEX_HOME:-$HOME/.codex}/skills" && ln -sfn "$(pwd)/skills/fastcontext-explorer" "${CODEX_HOME:-$HOME/.codex}/skills/fastcontext-explorer"
```

## Why This Exists

Microsoft FastContext separates repository exploration from code solving. The
upstream project describes a dedicated explorer that uses read-only `READ`,
`GLOB`, and `GREP` tools, issues parallel tool calls, and returns compact
`` citations. Microsoft reports Mini-SWE-Agent integration gains
of up to 5.5 score improvement and up to 60% main-agent token reduction.

Primary sources:

- Microsoft FastContext: 
- Model card: 
- Paper: 

## Quick Install

```bash
git clone https://github.com/Jakevin/fastcontext-agent-tools
cd fastcontext-agent-tools
python -m pip install -e .
python -m fastcontext_mcp --print-health
```

If your Python scripts directory is on `PATH`, `fastcontext-mcp --print-health`
works too.

## Requirements

- Python 3.12+.
- An OpenAI-compatible endpoint serving a FastContext-compatible model.

Installing this package also installs Microsoft FastContext from the pinned
official source revision. No separate FastContext checkout or CLI installation
is required.

Endpoint environment:

```bash
export BASE_URL="http://127.0.0.1:30000/v1"
export MODEL="microsoft/FastContext-1.0-4B-SFT"
export API_KEY="your-api-key"
export FASTCONTEXT_ALLOWED_ROOTS="/path/to/repos"
```

`FASTCONTEXT_ALLOWED_ROOTS` is an `os.pathsep` separated allowlist. If unset,
the MCP server only allows repositories under the directory where the server was
started.

## MCP Configuration

Example stdio config:

```json
{
  "mcpServers": {
    "fastcontext": {
      "command": "python",
      "args": ["-m", "fastcontext_mcp"],
      "env": {
        "BASE_URL": "http://127.0.0.1:30000/v1",
        "MODEL": "microsoft/FastContext-1.0-4B-SFT",
        "API_KEY": "your-api-key",
        "FASTCONTEXT_ALLOWED_ROOTS": "/path/to/repos"
      }
    }
  }
}
```

Localized MCP guides:

- Traditional Chinese: [docs/mcp.zh-TW.md](docs/mcp.zh-TW.md)
- Japanese: [docs/mcp.ja.md](docs/mcp.ja.md)

## MCP Tools

### `fastcontext_health`

Checks whether the bundled `fastcontext.cli` module is importable and whether
the endpoint environment is set.

### `fastcontext_explore`

Runs FastContext against a repository and returns parsed citations plus raw
output.

```json
{
  "repo_path": "/path/to/repo",
  "query": "Locate the request validation logic for uploaded files",
  "max_turns": 6,
  "citation": true,
  "timeout_seconds": 300
}
```

### `fastcontext_explore_with_trace`

Same as `fastcontext_explore`, but saves a FastContext JSONL trajectory. Relative
`trajectory_path` values are resolved inside `repo_path`.

## Codex Skill

The bundled skill lives at:

```text
skills/fastcontext-explorer
```

Install by copying or symlinking that folder into your Codex skills directory:

```bash
mkdir -p "${CODEX_HOME:-$HOME/.codex}/skills"
ln -s "$(pwd)/skills/fastcontext-explorer" "${CODEX_HOME:-$HOME/.codex}/skills/fastcontext-explorer"
```

Use the skill when a coding task requires repository localization before
editing. FastContext citations are candidate evidence; the main agent should
still read the cited files before changing code.

Additional project report:

- Full report: [docs/REPORT.md](docs/REPORT.md)

## Development

Run tests:

```bash
PYTHONPATH=src python -m unittest discover -s tests
```

Validate the bundled Codex skill:

```bash
python /path/to/skill-creator/scripts/quick_validate.py skills/fastcontext-explorer
```

## Safety Notes

- The MCP server exposes no edit/write tools.
- `repo_path` must resolve under `FASTCONTEXT_ALLOWED_ROOTS`.
- Secrets are read from environment variables only.
- Trajectories are written only when requested.

## License

MIT

## Source & license

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

- **Author:** [Jakevin](https://github.com/Jakevin)
- **Source:** [Jakevin/fastcontext-agent-tools](https://github.com/Jakevin/fastcontext-agent-tools)
- **License:** MIT

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-jakevin-fastcontext-agent-tools
- Seller: https://agentstack.voostack.com/s/jakevin
- Browse the marketplace: https://agentstack.voostack.com/browse

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