Backend Engineer - AI Agents (all genders)

Lime (Connect & CRM); Köln; On-site; EUR 90,000 - 120,000; Full time

Benefits offered by this job

600 € health budget

Urban Sports Club membership

Learning budget

Free Udemy/Masterclass access

Leadership programmes

Team events

Job summary

Lime Connect is seeking a backend-focused AI engineer to advance our AI agents. You will handle the agent loop, tool calling, and context management, while ensuring architecture supports seamless language-model switching.

You will drive evals to prove improvements before live deployment and implement feedback from service teams. You will also integrate APIs, MCP tools and web crawling to ensure the agents have the right knowledge and tools.

Qualifications

• Around five years of backend development, including at least a year building language-model features.
• Experience building AI agents and understanding context windows, tool calling and prompting.
• Hands-on with RAG and vector databases.
• Experience with evals (Langfuse, Arize Phoenix, LangSmith or similar).

Responsibilities

• Build and improve AI agents, including agent loop, tool calling, and context management.
• Set up architecture to switch language models without rebuilding everything.
• Use evals to verify improvements before live deployment.
• Translate feedback from service teams into concrete improvements.
• Connect APIs, MCP tools and website crawling for knowledge and tooling.
• Collaborate with the backend team and Product.

Skills

Backend development

Language-model features

RAG and vector DBs

Eval systems

German & English

Job description

What You’ll Be Working OnAt Lime Connect, AI agents already handle customer service conversations for our clients. Now we want to make them better: measurably, and regardless of which language model is currently ahead. That's why we're looking for someone with a backend background who feels at home in the AI world:

• You build and improve our AI agents, from the agent loop and tool calling to context management.
• You set up our architecture so we can switch language models without rebuilding everything.
• Before anything goes live, you use evals to check whether it's actually better. For example, with LLM-as-a-judge and test cases from real customer conversations.
• You turn feedback from the service teams working with our agents into concrete improvements. That way, the system keeps getting better step by step.
• You connect APIs, MCP tools and website crawling, so our agents have the right knowledge and the right tools.
• Within the backend team, you're the go-to person for AI and work closely with Product.

What Makes You a Fit

• Around five years of backend development, including at least a year building language-model features that real users rely on.
• You've built AI agents before and know what context windows, tool calling and prompting mean in practice.
• You've worked hands-on with RAG and vector databases.
• You have experience with evals, for example with Langfuse, Arize Phoenix or LangSmith, or you've built something similar yourself.
• Ideally, you know Pydantic AI, LiteLLM or similar libraries.
• You follow what's happening in AI, try new things quickly and take ownership of your topics.
• You speak German and English fluently.

What's in It for YouHEALTH & SPORTS

• 600 € health budget per year, including 24/7 medical advice — also for family members in your household
• Subsidised Urban Sports Club membership (20 € monthly contribution)

DEVELOPMENT & GROWTH

• Learning budget for courses, books and conferences
• Free access to Udemy, Masterclass and language learning apps
• Leadership programmes such as "Next Gen" and "Effective Manager"

TEAM & CULTURE

• Weekly FIKA, movie nights, book club and regular get-togethers and team events
• International summer party together with our colleagues in the Nordics

WORK ENVIRONMENT

• Office-first setup: 3 days in our Cologne office at the MediaPark, 2 days remote
• 360° view across Cologne from the 14th floor
• Workation within the EU
• Snacks, cereal bar and drinks in the office

COMPENSATION & BENEFITS

• Company pension scheme via Zurich with a 30 % employer contribution
• Job ticket or mobility budget, plus free parking at the MediaPark
• Corporate benefits
• 28 days of holiday, plus Christmas Eve and New Year's Eve off
• Up to 5 days of special leave for important life events

About usAutomated where it makes sense. Personal where it counts.

We are Lime Connect – an AI-first company and one of the top software scale-ups in Cologne. AI isn't an add-on for us, it's the core of what we build: our leading customer messaging solution for customer service, sales, and marketing combines AI agents, web chat, and mobile messaging, already automating the majority of all customer inquiries today. As part of Lime Technologies, our Swedish parent company, we combine international perspectives with the drive of a company actively shaping its next stage of growth. With us, you help shape things, not just execute them – with real ownership from day one, in a dynamic environment, and a culture that values results just as much as people. … Weekly fika included.