Software Engineer - Developer Experience / Agent Experience (Node.js)

About Sinch

Sinch is pioneering the way the world communicates. More than 150,000 businesses — including Google, Uber, PayPal, Visa, Tinder, and many others — rely on Sinch’s Customer Communications Cloud to power engaging customer experiences through mobile messaging, voice, and email.

Whether you need to verify users or craft omnichannel campaigns, Sinch makes it easy. Our AI-infused Super Network, APIs, and applications ensure you can connect with your customers reliably and securely, at every step of their journey.

At Sinch we “Dream Big”, “Win Together”, “Keep it simple”, and “Make it Happen”. These values are our foundation!

About the role

As a Software Engineer in our Developer Experience (DX) organization, you will play a key role in building and evolving our MCP server , which is a central piece of how Sinch APIs are discovered, understood, and consumed by external developers and agentic platforms.

This is not a traditional backend product role. You will be working on developer-facing infrastructure that connects APIs, SDKs, and documentation into a cohesive and consistent experience, with a strong focus on standards, interoperability, and agentic consumption.

Your work will be used directly by external developers, AI agents, and third-party frameworks . You care about what makes APIs and platforms pleasant to integrate with, and you enjoy thinking about developer ergonomics, consistency, and correctness.

This role is open to candidates based in Spain , from our offices in Madrid .

What you will do

As a Software Engineer, you will:

Be a core contributor to our MCP server , participating in its design, implementation, and long-term evolution, with increasing ownership over time.
Design and implement Node.js / TypeScript services that expose Sinch APIs in a way that is discoverable, standards-compliant, and easy to consume by developers and agentic frameworks.
Collaborate closely with Product Management, SDK engineers, and documentation teams to ensure a cohesive developer and agent experience across APIs, SDKs, and MCP.
Contribute in the definition and implement API standards, schemas, and validation mechanisms that ensure consistency and high quality across integrations.
Build and maintain authentication, authorization, and configuration suitable for external developer and agentic usage.
Ensure good levels of reliability, observability, and test coverage for a platform that external developers depend on.
Actively gather feedback from internal teams and external usage to continuously improve the MCP server and developer workflows.
Take part in architectural discussions around agentic protocols, emerging standards, and ecosystem integrations , learning and growing in this space with the team.

Requirements

5+ years of professional software development experience, with strong focus on Node.js and TypeScript .
Solid experience designing and building backend services and APIs .
Good understanding of REST APIs , API contracts, and schema-driven development.
Experience working on developer-facing platforms , tooling, or infrastructure, or strong interest in this type of work.
Familiarity with API authentication patterns , and configuration management.
Experience with testing strategies , CI/CD pipelines, and production-grade systems.
Comfort working in a role where developer experience and usability are key success metrics.
Fluent English, both written and spoken.

Nice to have

Experience with MCP , OpenAPI, or similar API description and discovery standards.
Exposure to agentic frameworks (e.g. LangChain, ADK) or AI-enabled developer tools.
Experience developing or maintaining SDKs, libraries, or developer tooling
Knowledge of schema validation or contract-first approaches (e.g. Zod ).
Experience working across multiple languages or SDK ecosystems (e.g. .NET, Java, Python).
Strong written communication skills, especially in technical documentation or design proposals.
Excellent problem-solving skills and attention to detail.

How you work

You have opinions about what makes a good API and a good developer experience , but you’re open to discussion and feedback.
You think in terms of systems and ecosystems , not just individual services.
You care about long-term maintainability and standards , not quick fixes.
You’re comfortable operating at the intersection of platform engineering , product thinking , and developer experience .
You enjoy working closely with product counterparts and influencing direction through technical contributions.

What we don’t expect

We don’t expect you to:

Be an expert in all agentic frameworks, protocols, or standards from day one.
Have prior experience with MCP specifically: the ability to learn and reason about new standards matters more than prior exposure.
Work in isolation or own everything alone: this role is highly collaborative and supported by peers across Product, SDK, and Platform teams.
Be a pure feature-delivery backend developer: success here is measured by usability, consistency, and adoption, not just output.
Have perfect answers upfront: we value curiosity, good judgment, and the ability to iterate and improve designs over time.

Why this role matters

The MCP server is a strategic pillar for Sinch’s API and agentic platform ambitions. Success in this role directly impacts:

How easily developers and agents discover and adopt Sinch APIs
How consistent and trustworthy our API ecosystem feels
How well Sinch positions itself as a developer-first, agent-ready platform

You will be building infrastructure that defines how the outside world experiences Sinch .

Our Hiring Process

We are committed to ensuring a recruitment process that is fair, objective, consistent, and inclusive. Our approach includes structured, competency-based interviews designed to evaluate your skills, experience, and qualifications relevant to the role. At times, we may include a data-driven assessment to enhance our hiring success and identify candidates likely to excel.

We believe in a two-way process and encourage you to ask questions throughout the journey. If this role isn't what you're looking for, please explore the other opportunities listed on our career page: https://www.sinch.com/careers/ . No matter who you are, we hope you find an exciting path forward - hopefully with us!

Please send your CV in English language.