npm package: @sisu-ai/mw-react-parser
Description: Run lightweight ReAct-style loops when you want plain-text action parsing and tool execution.
Latest version: 12.0.0

# @sisu-ai/mw-react-parser

Run lightweight ReAct-style loops when you want plain-text action parsing and tool execution.

[![Tests](https://github.com/finger-gun/sisu/actions/workflows/tests.yml/badge.svg?branch=main)](https://github.com/finger-gun/sisu/actions/workflows/tests.yml)
[![CodeQL](https://github.com/finger-gun/sisu/actions/workflows/github-code-scanning/codeql/badge.svg)](https://github.com/finger-gun/sisu/actions/workflows/github-code-scanning/codeql)
[![License](https://img.shields.io/badge/license-Apache--2.0-blue)](https://github.com/finger-gun/sisu/blob/main/LICENSE)
[![Downloads](https://img.shields.io/npm/dm/%40sisu-ai%2Fmw-react-parser)](https://www.npmjs.com/package/@sisu-ai/mw-react-parser)
[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](https://github.com/finger-gun/sisu/blob/main/CONTRIBUTING.md)

## Setup
```bash
npm i @sisu-ai/mw-react-parser
```

## Exports
- `reactToolLoop()` — returns middleware that performs one ReAct cycle as described.

## What It Does
- Think → Act → Observe → Reflect loop without provider‑specific function calling.
- Parses `Action: <tool>` and `Action Input: <json or text>` from the assistant’s message.
- Invokes a registered tool, feeds the observation back, and asks the model for a final answer.

## How It Works
- Calls `model.generate(..., { toolChoice: 'none' })` to get an initial assistant message.
- Extracts `tool` and `args` via regex; attempts `JSON.parse` on the input, falls back to raw text.
- Executes the tool and appends a user message like `Observation (tool): <result>`.
- Calls `model.generate` again (tools still disabled) and pushes the final assistant message.

This keeps the loop adapter‑agnostic and easy to reason about at the cost of relying on formatting.

## Usage
```ts
import 'dotenv/config';
import { Agent, createConsoleLogger, InMemoryKV, NullStream, SimpleTools, type Ctx } from '@sisu-ai/core';
import { openAIAdapter } from '@sisu-ai/adapter-openai';
import { registerTools } from '@sisu-ai/mw-register-tools';
import { inputToMessage } from '@sisu-ai/mw-conversation-buffer';
import { reactToolLoop } from '@sisu-ai/mw-react-parser';

const model = openAIAdapter({ model: 'gpt-5.4' });

// Example tool
const webSearch = {
  name: 'webSearch',
  description: 'Search the web for a query',
  schema: { type: 'object', properties: { q: { type: 'string' } }, required: ['q'] },
  handler: async ({ q }: { q: string }) => ({ top: [`Result for ${q}`] })
};

const ctx: Ctx = {
  input: 'Find the npm page for @sisu-ai/core then summarize.',
  messages: [{ role: 'system', content: 'When helpful, decide an action using:\nAction: <tool>\nAction Input: <JSON>. Then reflect with the observation.' }],
  model,
  tools: new SimpleTools(),
  memory: new InMemoryKV(),
  stream: new NullStream(),
  state: {},
  signal: new AbortController().signal,
  log: createConsoleLogger({ level: 'info' })
};

const app = new Agent()
  .use(registerTools([webSearch as any]))
  .use(inputToMessage)
  .use(reactToolLoop());
```

### Prompting Tips
- Seed the system prompt with the required format, e.g.:
  - `Use tools when helpful. Reply with:\nAction: <tool>\nAction Input: <JSON>`
- Keep tool schemas strict and arguments small to make parsing robust.

## When To Use
- You want a provider‑agnostic tool loop that works with any chat model.
- You need a simple ReAct cycle without native function calling.

## When Not To Use
- You rely on provider‑native tools/function‑calling — prefer `@sisu-ai/mw-tool-calling` instead.
- You need multi‑step or iterative planning — use `iterativeToolCalling` or a planner middleware.

## Notes & Gotchas
- Formatting sensitivity: parsing uses regex; poor formatting may fail to extract the action.
- Security: validate tool inputs (zod) and guard tools with allow‑lists/capabilities.
- Streaming: this middleware uses non‑streaming `generate` calls; pair with a streaming middleware if you need live tokens.

# Community & Support

Discover what you can do through examples or documentation. Check it out at https://github.com/finger-gun/sisu. Example projects live under [`examples/`](https://github.com/finger-gun/sisu/tree/main/examples) in the repo.

- [Code of Conduct](https://github.com/finger-gun/sisu/blob/main/CODE_OF_CONDUCT.md)
- [Contributing Guide](https://github.com/finger-gun/sisu/blob/main/CONTRIBUTING.md)
- [License](https://github.com/finger-gun/sisu/blob/main/LICENSE)
- [Report a Bug](https://github.com/finger-gun/sisu/issues/new?template=bug_report.md)
- [Request a Feature](https://github.com/finger-gun/sisu/issues/new?template=feature_request.md)

---

## Documentation

**Core** — [Package docs](packages/core/README.md) · [Error types](packages/core/ERROR_TYPES.md)

**Adapters** — [OpenAI](packages/adapters/openai/README.md) · [Anthropic](packages/adapters/anthropic/README.md) · [Ollama](packages/adapters/ollama/README.md)

<details>
<summary>All middleware packages</summary>

- [@sisu-ai/mw-agent-run-api](packages/middleware/agent-run-api/README.md)
- [@sisu-ai/mw-context-compressor](packages/middleware/context-compressor/README.md)
- [@sisu-ai/mw-control-flow](packages/middleware/control-flow/README.md)
- [@sisu-ai/mw-conversation-buffer](packages/middleware/conversation-buffer/README.md)
- [@sisu-ai/mw-cors](packages/middleware/cors/README.md)
- [@sisu-ai/mw-error-boundary](packages/middleware/error-boundary/README.md)
- [@sisu-ai/mw-guardrails](packages/middleware/guardrails/README.md)
- [@sisu-ai/mw-invariants](packages/middleware/invariants/README.md)
- [@sisu-ai/mw-orchestration](packages/middleware/orchestration/README.md)
- [@sisu-ai/mw-rag](packages/middleware/rag/README.md)
- [@sisu-ai/mw-react-parser](packages/middleware/react-parser/README.md)
- [@sisu-ai/mw-register-tools](packages/middleware/register-tools/README.md)
- [@sisu-ai/mw-tool-calling](packages/middleware/tool-calling/README.md)
- [@sisu-ai/mw-trace-viewer](packages/middleware/trace-viewer/README.md)
- [@sisu-ai/mw-usage-tracker](packages/middleware/usage-tracker/README.md)
</details>

<details>
<summary>All tool packages</summary>

- [@sisu-ai/tool-aws-s3](packages/tools/aws-s3/README.md)
- [@sisu-ai/tool-azure-blob](packages/tools/azure-blob/README.md)
- [@sisu-ai/tool-extract-urls](packages/tools/extract-urls/README.md)
- [@sisu-ai/tool-github-projects](packages/tools/github-projects/README.md)
- [@sisu-ai/tool-rag](packages/tools/rag/README.md)
- [@sisu-ai/tool-summarize-text](packages/tools/summarize-text/README.md)
- [@sisu-ai/tool-terminal](packages/tools/terminal/README.md)
- [@sisu-ai/tool-web-fetch](packages/tools/web-fetch/README.md)
- [@sisu-ai/tool-web-search-duckduckgo](packages/tools/web-search-duckduckgo/README.md)
- [@sisu-ai/tool-web-search-google](packages/tools/web-search-google/README.md)
- [@sisu-ai/tool-web-search-openai](packages/tools/web-search-openai/README.md)
- [@sisu-ai/tool-wikipedia](packages/tools/wikipedia/README.md)
</details>

<details>
<summary>All RAG packages</summary>

- [@sisu-ai/rag-core](packages/rag/core/README.md)
</details>

<details>
<summary>All vector packages</summary>

- [@sisu-ai/vector-core](packages/vector/core/README.md)
- [@sisu-ai/vector-chroma](packages/vector/chroma/README.md)
</details>

<details>
<summary>All examples</summary>

**Anthropic** — [hello](examples/anthropic-hello/README.md) · [control-flow](examples/anthropic-control-flow/README.md) · [stream](examples/anthropic-stream/README.md) · [weather](examples/anthropic-weather/README.md)

**Ollama** — [hello](examples/ollama-hello/README.md) · [stream](examples/ollama-stream/README.md) · [vision](examples/ollama-vision/README.md) · [weather](examples/ollama-weather/README.md) · [web-search](examples/ollama-web-search/README.md)

**OpenAI** — [hello](examples/openai-hello/README.md) · [weather](examples/openai-weather/README.md) · [stream](examples/openai-stream/README.md) · [vision](examples/openai-vision/README.md) · [reasoning](examples/openai-reasoning/README.md) · [react](examples/openai-react/README.md) · [control-flow](examples/openai-control-flow/README.md) · [branch](examples/openai-branch/README.md) · [parallel](examples/openai-parallel/README.md) · [graph](examples/openai-graph/README.md) · [orchestration](examples/openai-orchestration/README.md) · [orchestration-adaptive](examples/openai-orchestration-adaptive/README.md) · [guardrails](examples/openai-guardrails/README.md) · [error-handling](examples/openai-error-handling/README.md) · [rag-chroma](examples/openai-rag-chroma/README.md) · [web-search](examples/openai-web-search/README.md) · [web-fetch](examples/openai-web-fetch/README.md) · [wikipedia](examples/openai-wikipedia/README.md) · [terminal](examples/openai-terminal/README.md) · [github-projects](examples/openai-github-projects/README.md) · [server](examples/openai-server/README.md) · [aws-s3](examples/openai-aws-s3/README.md) · [azure-blob](examples/openai-azure-blob/README.md)
</details>

---

## Contributing

We build Sisu in the open. Contributions welcome.

[Contributing Guide](CONTRIBUTING.md) · [Report a Bug](https://github.com/finger-gun/sisu/issues/new?template=bug_report.md) · [Request a Feature](https://github.com/finger-gun/sisu/issues/new?template=feature_request.md) · [Code of Conduct](CODE_OF_CONDUCT.md)

---

<div align="center">

**[Star on GitHub](https://github.com/finger-gun/sisu)** if Sisu helps you build better agents.

*Quiet, determined, relentlessly useful.*

[Apache 2.0 License](LICENSE)

</div>