Comparisons / Anthropic Agent SDK vs Haystack
Anthropic Agent SDK vs Haystack: Which Agent Framework to Use?
The Anthropic Agent SDK packages Claude Code's agent loop as a library. Haystack by deepset is a framework for building NLP and LLM pipelines. Here is how they compare — paradigm, ecosystem, and the use cases each one is actually built for.
By the numbers
Anthropic Agent SDK
3.1k
582
Python
MIT
2023-01-17
Anthropic
Google, Spark Capital
Yes
Haystack
24.7k
2.7k
Python
Apache-2.0
2019-11-14
deepset
GitHub stats as of April 2026. Stars indicate community interest, not necessarily quality or fit for your use case.
| Concept | Anthropic Agent SDK | Haystack |
|---|---|---|
| Agent | Claude agent with built-in tools, MCP servers, and system prompt | `Agent` component with `ChatGenerator`, tool definitions, and message routing |
| Tools | Built-in tools (`bash`, file read/write, web) + MCP server connections | `Tool` dataclass with function reference, name, description, parameters schema |
| Agent Loop | SDK's internal agentic loop with automatic tool dispatch | — |
| Sub-Agents | Agents invoke other agents as tools via the SDK | — |
| Lifecycle Hooks | 18 hook events: pre/post tool call, message, error, etc. | — |
| MCP Integration | One-line MCP server config for Playwright, Slack, GitHub, etc. | — |
| Pipeline Architecture | — | `Pipeline()` with `add_component()` and `connect()` — a directed graph of typed components |
| RAG / Retrieval | — | `DocumentStore` + `Retriever` + `PromptBuilder` + `Generator` wired in a `Pipeline` |
| Memory | — | `ChatMessageStore` with `ConversationMemory` component in pipeline |
| Deployment | — | Pipeline YAML serialization, `Hayhooks` REST server |
Anthropic Agent SDK vs Haystack, head to head
Anthropic Agent SDK The Anthropic Agent SDK packages Claude Code's agent loop as a library.
Haystack Haystack by deepset is a framework for building NLP and LLM pipelines.
Both wrap the same underlying agent pattern — an LLM call, a tool dispatch, a loop — in different abstractions. The choice between them is mostly about which mental model and ecosystem fits the team you have, not which one is technically more capable.
Pick Anthropic Agent SDK if
Pick Anthropic Agent SDK if the Anthropic Agent SDK's real value is packaging Claude Code's battle-tested agent loop with built-in tools and MCP integration. If you want a production agent that reads files, runs commands, and connects to services, it saves significant plumbing. For understanding how agents work, the plain version is more instructive. Anthropic Agent SDK is the right fit when the tradeoffs in its intro line up with how your team actually wants to work day-to-day; Haystack would force you to translate.
Pick Haystack if
Pick Haystack if haystack earns its complexity when you're building RAG pipelines with multiple retrieval stages, document processing, and production deployment needs. But for straightforward agents with a few tools, the plain Python version is simpler to write and debug. Haystack is the right fit when the tradeoffs in its intro line up with how your team actually wants to work day-to-day; Anthropic Agent SDK would force you to translate.
What both add
Both Anthropic Agent SDK and Haystack pull in a class hierarchy and a dependency tree to wrap what is, at the core, an HTTP POST in a while loop. If your use case is straightforward — one provider, a handful of tools, a single agent — the framework cost may exceed the framework benefit. The lesson below shows the same pattern in ~60 lines without either dependency.
Or build your own in 60 lines
Both Anthropic Agent SDK and Haystack implement the same 8 patterns. An agent is a function. Tools are a dict. The loop is a while loop. The whole thing composes in ~60 lines of Python.
No framework. No dependencies. No opinions. Just the code.
Build it from scratch →