chuk-tool-processor 0.15

Async-native framework for registering, discovering, and executing tools referenced in LLM responses

CHUK Tool Processor — A Tool Execution Runtime for AI Systems

Reliable tool execution for LLMs — timeouts, retries, caching, rate limits, circuit breakers, and MCP integration — in one composable layer.

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The Missing Runtime Layer

LLMs are good at deciding which tools to call. The hard part is executing those tools reliably.

CHUK Tool Processor is a tool execution runtime — it doesn't plan workflows or decide which tools to call. It executes tool calls reliably, under constraints, as directed by higher-level planners (your agent, LangChain, LlamaIndex, or a custom orchestrator).

What it does:

• Parses tool calls from any model (Anthropic XML, OpenAI tool_calls, JSON)
• Executes them with timeouts, retries, caching, rate limits, circuit breaker, observability
• Runs tools locally, in isolated subprocesses, or remote via MCP

Works with OpenAI, Anthropic, local models (Ollama/MLX/vLLM), and any framework.

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Architecture

    LLM Output
        ↓
CHUK Tool Processor
        ↓
 ┌──────────────┬────────────────────┐
 │ Local Tools  │ Remote Tools (MCP) │
 └──────────────┴────────────────────┘

How it works internally:

    LLM Output
        ↓
Parsers (XML / OpenAI / JSON)
        ↓
┌─────────────────────────────┐
│   Execution Middleware      │
│  (Applied in this order)    │
│   • Cache                   │
│   • Rate Limit              │
│   • Retry (with backoff)    │
│   • Circuit Breaker         │
│   • Bulkhead                │
└─────────────────────────────┘
        ↓
   Execution Strategy
   ┌──────────────────────┐
   │ • InProcess          │  ← Fast, trusted
   │ • Isolated/Subprocess│  ← Safe, untrusted
   │ • Remote via MCP     │  ← Distributed
   └──────────────────────┘

---

Quick Start

Installation

pip install chuk-tool-processor

# Or with uv (recommended)
uv pip install chuk-tool-processor

60-Second Example

import asyncio
from chuk_tool_processor import ToolProcessor, create_registry

class Calculator:
    async def execute(self, operation: str, a: float, b: float) -> dict:
        ops = {"add": a + b, "multiply": a * b, "subtract": a - b}
        return {"result": ops.get(operation, 0)}

async def main():
    registry = create_registry()
    await registry.register_tool(Calculator, name="math.calculator")  # Dotted name → namespace="math"

    async with ToolProcessor(registry=registry, enable_caching=True, enable_retries=True) as p:
        # Works with OpenAI, Anthropic, or JSON formats
        result = await p.process('<tool name="math.calculator" args=\'{"operation": "multiply", "a": 15, "b": 23}\'/>')
        print(result[0].result)  # {'result': 345}

asyncio.run(main())

That's it. You now have production-ready tool execution with timeouts, retries, and caching.

Dotted Names for Namespacing

Dotted names are auto-parsed into namespace and tool name:

# These are equivalent:
await registry.register_tool(FetchUser, name="web.fetch_user")           # Auto-parsed
await registry.register_tool(FetchUser, name="fetch_user", namespace="web")  # Explicit

# Call using the full dotted name
result = await processor.process([{"tool": "web.fetch_user", "arguments": {"user_id": "123"}}])

Works with Any LLM Format

# Anthropic XML format
anthropic_output = '<tool name="search" args=\'{"query": "Python"}\'/>'

# OpenAI tool_calls format
openai_output = {
    "tool_calls": [{
        "type": "function",
        "function": {"name": "search", "arguments": '{"query": "Python"}'}
    }]
}

# Direct JSON
json_output = [{"tool": "search", "arguments": {"query": "Python"}}]

# All work identically
results = await processor.process(anthropic_output)
results = await processor.process(openai_output)
results = await processor.process(json_output)

---

Key Features

Production Reliability

Feature	Description
Timeouts	Every tool execution has proper timeout handling
Retries	Automatic retry with exponential backoff and jitter
Rate Limiting	Global and per-tool rate limits with sliding windows
Caching	Result caching with TTL and SHA256-based idempotency keys
Circuit Breakers	Prevent cascading failures with automatic recovery

Multi-Tenant & Isolation

Feature	Description
Bulkheads	Per-tool/namespace concurrency limits to prevent resource starvation
Pattern Bulkheads	Glob patterns like "db.*": 3 for grouped concurrency limits
Scoped Registries	Isolated registries for multi-tenant apps and testing
ExecutionContext	Request-scoped metadata propagation (user, tenant, tracing, deadlines)
Isolated Strategy	Subprocess execution for untrusted code (zero crash blast radius)

Advanced Scheduling

Feature	Description
Return Order	Choose completion order (fast first) or submission order (deterministic)
SchedulerPolicy	DAG-based scheduling with dependencies, deadlines, pool limits
GreedyDagScheduler	Built-in scheduler with topological sort and deadline-aware skipping

Integration & Observability

Feature	Description
Multi-Format Parsing	XML (Anthropic), OpenAI tool_calls, JSON — all work automatically
MCP Integration	Connect to remote tools via HTTP Streamable, STDIO, SSE
OpenTelemetry	Distributed tracing with automatic span creation
Prometheus	Metrics for error rates, latency, cache hits, circuit breaker state
Type Safety	PEP 561 compliant with full mypy support

---

Production Configuration

async with ToolProcessor(
    # Execution settings
    default_timeout=30.0,
    max_concurrency=20,

    # Reliability features
    enable_caching=True,
    cache_ttl=600,
    enable_rate_limiting=True,
    global_rate_limit=100,
    tool_rate_limits={"expensive_api": (5, 60)},  # 5 req/min
    enable_retries=True,
    max_retries=3,
    enable_circuit_breaker=True,
    circuit_breaker_threshold=5,

    # Multi-tenant isolation
    enable_bulkhead=True,
    bulkhead_config=BulkheadConfig(
        default_limit=10,
        tool_limits={"slow_api": 2},
        patterns={"db.*": 3, "mcp.notion.*": 2},  # Pattern-based limits
    ),
) as processor:
    # Execute with request context
    ctx = ExecutionContext(
        request_id="req-123",
        user_id="user-456",
        tenant_id="acme-corp",
    )
    results = await processor.process(llm_output, context=ctx)

---

Return Order & Scheduling

Control how results are returned and plan complex execution graphs:

from chuk_tool_processor import ToolProcessor, ReturnOrder

async with ToolProcessor() as processor:
    # Results return as tools complete (fast tools first) - default
    results = await processor.process(calls, return_order="completion")

    # Results return in submission order (deterministic)
    results = await processor.process(calls, return_order="submission")

DAG Scheduling with Dependencies

from chuk_tool_processor import (
    GreedyDagScheduler,
    SchedulingConstraints,
    ToolCallSpec,
    ToolMetadata,
)

scheduler = GreedyDagScheduler()

# Define calls with dependencies
calls = [
    ToolCallSpec(call_id="fetch", tool_name="api.fetch",
                 metadata=ToolMetadata(pool="web", est_ms=300)),
    ToolCallSpec(call_id="transform", tool_name="compute.transform",
                 depends_on=("fetch",)),
    ToolCallSpec(call_id="store", tool_name="db.write",
                 depends_on=("transform",)),
]

# Plan execution with constraints
constraints = SchedulingConstraints(
    deadline_ms=5000,
    pool_limits={"web": 2, "db": 1},
)
plan = scheduler.plan(calls, constraints)

# plan.stages: (('fetch',), ('transform',), ('store',))
# plan.skip: () or low-priority calls that would miss deadline

---

MCP Integration

Connect to remote tool servers using the Model Context Protocol:

from chuk_tool_processor.mcp import setup_mcp_http_streamable

# Cloud services (Notion, etc.)
processor, manager = await setup_mcp_http_streamable(
    servers=[{
        "name": "notion",
        "url": "https://mcp.notion.com/mcp",
        "headers": {"Authorization": f"Bearer {token}"}
    }],
    namespace="notion",
    enable_caching=True,
    enable_retries=True
)

# Use remote tools
results = await processor.process(
    '<tool name="notion.search_pages" args=\'{"query": "docs"}\'/>'
)

Transport Options:

Transport	Use Case	Example
HTTP Streamable	Cloud SaaS with OAuth	Notion, custom APIs
STDIO	Local tools, databases	SQLite, file systems
SSE	Legacy MCP servers	Atlassian

See MCP_INTEGRATION.md for complete examples with OAuth token refresh.

MCP Middleware Stack

For production deployments, wrap MCP connections with resilience middleware:

from chuk_tool_processor.mcp.middleware import (
    MiddlewareConfig,
    MiddlewareStack,
    RetrySettings,
    CircuitBreakerSettings,
    RateLimitSettings,
)

# Configure middleware layers
config = MiddlewareConfig(
    retry=RetrySettings(max_retries=3, base_delay=1.0),
    circuit_breaker=CircuitBreakerSettings(failure_threshold=5),
    rate_limiting=RateLimitSettings(enabled=True, global_limit=100),
)

# Wrap StreamManager with middleware
middleware = MiddlewareStack(stream_manager, config=config)

# Execute with automatic retry, circuit breaking, and rate limiting
result = await middleware.call_tool("notion.search", {"query": "docs"})

---

Observability

One-line setup for production monitoring:

from chuk_tool_processor.observability import setup_observability

setup_observability(
    service_name="my-tool-service",
    enable_tracing=True,     # → OpenTelemetry traces
    enable_metrics=True,     # → Prometheus metrics at :9090/metrics
    metrics_port=9090
)
# Every tool execution is now automatically traced and metered

What you get:

• Distributed traces (Jaeger, Zipkin, any OTLP collector)
• Prometheus metrics (error rate, latency P50/P95/P99, cache hit rate)
• Circuit breaker state monitoring
• Zero code changes to your tools

See OBSERVABILITY.md for complete setup guide.

---

Documentation

Document	Description
GETTING_STARTED.md	Creating tools, using the processor, ValidatedTool, StreamingTool
CORE_CONCEPTS.md	Registry, strategies, wrappers, parsers, MCP overview
PRODUCTION_PATTERNS.md	Bulkheads, scoped registries, ExecutionContext, parallel execution
MCP_INTEGRATION.md	HTTP Streamable, STDIO, SSE, OAuth, Middleware Stack
ADVANCED_TOPICS.md	Deferred loading, code sandbox, isolated strategy, testing
CONFIGURATION.md	All config options and environment variables
OBSERVABILITY.md	OpenTelemetry, Prometheus, metrics reference
ERRORS.md	Error codes and handling patterns

---

Examples

# Getting started
python examples/01_getting_started/hello_tool.py

# Hero demo: 8 tools, 5-second deadline, 3 pools (DAG + bulkheads + context)
python examples/02_production_features/hero_runtime_demo.py

# Production patterns (bulkheads, context, scoped registries)
python examples/02_production_features/production_patterns_demo.py

# Runtime features (return order, pattern bulkheads, scheduling)
python examples/02_production_features/runtime_features_demo.py

# Observability demo
python examples/02_production_features/observability_demo.py

# MCP integration
python examples/04_mcp_integration/stdio_echo.py
python examples/04_mcp_integration/notion_oauth.py
python examples/04_mcp_integration/middleware_demo.py

See examples/ for 20+ working examples.

---

Compatibility

Component	Supported
Python	3.11, 3.12, 3.13
Platforms	macOS, Linux, Windows
LLM Providers	OpenAI, Anthropic, Local models (Ollama, MLX, vLLM)
MCP Transports	HTTP Streamable, STDIO, SSE
MCP Spec	2025-11-25, 2025-06-18, 2025-03-26

---

Installation Options

# Core package
pip install chuk-tool-processor

# With observability (OpenTelemetry + Prometheus)
pip install chuk-tool-processor[observability]

# With MCP support
pip install chuk-tool-processor[mcp]

# With fast JSON (2-3x faster with orjson)
pip install chuk-tool-processor[fast-json]

# All extras
pip install chuk-tool-processor[all]

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When to Use This

Use CHUK Tool Processor when:

• Your LLM calls tools or APIs
• You need retries, timeouts, caching, or rate limits
• You need to run untrusted tools safely
• Your tools are local or remote (MCP)
• You need multi-tenant isolation
• You want production-grade observability

Don't use this if:

• You want an agent framework (this is the execution runtime, not the agent)
• You want conversation flow/memory orchestration
• You need a planner to decide which tools to call

The Seam: Runtime vs Planner

CHUK Tool Processor deliberately does not plan workflows or decide which tools to call. It executes tool calls reliably, under constraints, as directed by higher-level planners.

┌─────────────────────────────────────────────────────┐
│  Your Agent / LangChain / LlamaIndex / Custom       │  ← Decides WHICH tools
└─────────────────────────────────────────────────────┘
                          ↓
┌─────────────────────────────────────────────────────┐
│            CHUK Tool Processor                      │  ← Executes tools RELIABLY
│  (timeouts, retries, caching, rate limits, etc.)   │
└─────────────────────────────────────────────────────┘
                          ↓
┌─────────────────────────────────────────────────────┐
│          Local Tools / MCP Servers                  │  ← Does the actual work
└─────────────────────────────────────────────────────┘

This separation means you can swap planners without changing execution infrastructure, and vice versa.

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Contributing

See CONTRIBUTING.md for development setup and guidelines.

# Development setup
git clone https://github.com/chrishayuk/chuk-tool-processor.git
cd chuk-tool-processor
uv pip install -e ".[dev]"

# Run tests
make check

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License

MIT License - see LICENSE for details.

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Related Projects

• chuk-mcp - Low-level MCP protocol client
• Model Context Protocol - MCP specification