MCP CLI Development Engineer Intern

CaelumenAI; San Francisco (CA); On-site; USD 25,000 - 40,000; Full time

Job summary

Caelumen is seeking an MCP CLI Development Engineer Intern to contribute to the PERCO CLI and MCP integration surface. You will own small, real product slices across command design, client integration, reliability, documentation, and verification—from scoped problems to implementation and evidence-backed handoffs.

This remote-first internship offers mentorship and ownership over end-to-end engineering tasks, with flexible collaboration and the option to work from San Francisco.

Qualifications

• Proficiency in JavaScript, TypeScript or Python and Git.
• Familiarity with web or API fundamentals.

Responsibilities

• Build and improve the PERCO CLI and MCP connection workflow for coding clients.
• Design clear, reliable command flows for login, project linking, MCP installation, configuration, and recovery from errors.
• Implement and test developer-facing integrations across supported coding clients and real project environments.
• Make tool contracts predictable: explicit limits, safe inputs, and actionable error messages.
• Automate repeatable checks with unit and integration tests, Playwright, logs, and release evidence.
• Investigate failures to root cause and ship durable fixes with regression coverage.

Skills

JavaScript

TypeScript

Python

Git

Web fundamentals

API fundamentals

Job description

# MCP CLI Development Engineer InternBuild the MCP and CLI experience that lets coding agents connect to PERCO safely, understand project context, and prepare governed production work.Applications openLocation: Remote / San Francisco, CAWork model: Remote-firstEmployment: InternshipCompensation: Salary range shared in processApplication window: Open until filledApply for this role ↓01 / The role## Build the system, then prove it works.CaelumenAI is building the governed production layer for agent-native software. PERCO, our flagship product, turns agent output into a reviewable plan, a controlled release, and evidence of what happened.As an MCP CLI Development Engineer Intern, you will work directly on the PERCO CLI and its MCP integration surface: the developer experience that connects coding clients to the control plane. You will own small, real product slices across command design, client integration, reliability, documentation, and verification—from a clearly scoped problem through implementation, real-client testing, and an evidence-backed handoff.This is not an autopilot project. The tools should give agents useful context and safe, typed capabilities while keeping credentials, infrastructure authority, and final production decisions with people.Compensation: Salary range is not disclosed for this internship. We will discuss internship scope and compensation during the process.02 / Your work## What you’ll do* Build and improve the PERCO CLI and MCP connection workflow for coding clients* Design clear, reliable command flows for login, project linking, MCP installation, configuration, and recovery from errors* Implement and test developer-facing integrations across supported coding clients and real project environments* Make tool contracts predictable: useful project context, explicit limits, safe typed inputs, and actionable error messages* Automate repeatable checks with unit tests, integration tests, Playwright, command output, logs, and release evidence* Investigate failures to root cause and ship durable fixes with regression coverage03 / The signal## What we’re looking forEvidence over pedigreeShow us something you scoped, built, tested, and debugged—and tell us what the evidence changed.* One substantive developer-tool, CLI, integration, or open-source project you designed, built, tested, and debugged that you can explain in detail* Working proficiency in JavaScript or TypeScript or Python, Git, and web or API fundamentals* Comfort with command-line workflows, package tooling, configuration, and debugging across local development environments* Ability to turn ambiguous developer feedback into a small, testable product improvement* Comfort testing real user journeys, reading logs, and iterating until an integration works end to end* Clear written communication and a bias toward ownership, careful judgment, and evidence04 / Bonus signal## Useful, not required* Experience building with MCP, JSON-RPC, tool schemas, or agent integrations* Experience with coding clients such as Claude Code, Codex, Cursor, or similar developer tools* Experience publishing npm packages or building CLI setup, authentication, or configuration flows* Open-source contributions, developer documentation, or a shipped tool that other people use05 / What we offer## What you get* Direct mentorship on a real developer-facing product* High ownership over scoped, end-to-end engineering projects* Flexible remote collaboration with an option to work from San Francisco* Work at the intersection of MCP, coding agents, cloud systems, and responsible deliveryApplication## Apply for this roleTell us what you have built and how you know it worked. A concise application with real evidence is enough.