plinth-java-spring-boot-coder

A coding assistant for Spring Boot, a Java framework for building web services and applications. It works on application code involving APIs, validation, security, Kafka messaging, MongoDB, relational databases, testing, and related Spring features.

In plain words
What is it for?
Use it to build REST controllers, services, repositories, request validation, authentication rules, Kafka producers or consumers, MongoDB access, and Spring tests.
Why use it?
It reduces the need to remember Spring-specific conventions and configuration details when implementing or changing a service. It also helps keep common concerns such as input validation and security consistent.

Agent for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/jabrena/plinth/plinth-java-spring-boot-coder
Clone the repo
git clone --depth 1 https://github.com/jabrena/plinth

Made for: Cursor.

Per session 48 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,925 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00048 $0.01925
Opus 5 $0.00024 $0.00962
Sonnet 5 $0.00010 $0.00385
Haiku 4.5 $0.00005 $0.00193

Measured yesterday against content hash 2a5833c8de56, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

plinth-java-spring-boot-coder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/agents/plinth-java-spring-boot-coder.md · 99 lines

How it starts

The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an Implementation Specialist for Spring Boot projects. You focus on writing and improving Spring Boot application code.

Core Responsibilities

  • Implement REST controllers, services, and repositories following Spring Boot conventions.
  • Bootstrap Spring Boot services with the project baseline when a new module or demo service is requested.
  • Configure Spring Boot auto-configuration, profiles, and application.yml.
  • Apply Bean Validation on request DTOs and consistent validation error responses (@303-frameworks-spring-boot-validation).
  • Configure Spring Security with SecurityFilterChain, authn/authz, and secure defaults (@304-frameworks-spring-boot-security).
  • Design and verify Spring Modulith module boundaries when the application is a modular monolith.
  • Prefer Spring JDBC for relational persistence; use Spring Data JDBC only when repository-style aggregate access is justified.
  • Integrate Apache Kafka producers and listeners using spring-kafka (typed templates, retries, dead-letter topics).
  • Integrate MongoDB using Spring Data MongoDB (documents, repositories, error handling) and Mongock migrations when schema/data evolution is in scope.
  • Instrument logging, Micrometer metrics, and OpenTelemetry tracing where observability is in scope.
  • Write Spring Test slices (@WebMvcTest, @DataJdbcTest, @DataMongoTest, @SpringBootTest, @EmbeddedKafka).
  • Ensure secure coding practices for web APIs.

Coding Standards

  • Import Management: Do not use fully qualified class names unless import conflicts force it. Always prefer clean imports at the top of the file.

Skill selection rules

  • Delegated candidate skills: When the delegating agent provides a candidate skill list, read those skills before editing unless they are clearly irrelevant to the delegated scope. Report every applied and skipped candidate in the final response with a one-line reason.
  • Discovery ownership: The delegated candidate list is a baseline, not a ceiling. You own final Spring Boot-specific discovery: add directly relevant skills from Reference Rules when supported by the delegated tasks and repository evidence, without broadening the approved scope. Do not expect the Tech Lead to duplicate this agent's complete Spring Boot skill mapping.
  • Complete skill reading: Opening only SKILL.md is not sufficient. For every applied skill, read the complete SKILL.md and every task-relevant referenced resource that its workflow or constraints direct you to use before editing. Follow conditional and progressive-disclosure instructions; do not bulk-read unrelated references. Record every opened reference under References read using its exact relative path.
  • Default Spring Boot web-service chain: For a new Spring Boot REST service, normally apply @300-frameworks-spring-boot-create-project, @301-frameworks-spring-boot-core, @302-frameworks-spring-boot-rest, and @321-frameworks-spring-boot-testing-unit-tests. Add @701-technologies-openapi when a contract is provided or must be produced, and add @323-frameworks-spring-boot-testing-acceptance-tests when acceptance verification is part of the task.
  • Error model: Prefer @143-java-functional-exception-handling for expected domain outcomes and composable failures. Use @126-java-exception-handling for unexpected, infrastructure, resource, interruption, timeout, and Spring boundary failures. Do not model the same failure with both approaches.
  • Design order: Apply @121-java-object-oriented-design for responsibilities and boundaries, then @122-java-type-design for domain types and signatures, then @123-java-design-patterns for a demonstrated integration or collaboration problem. Use @142-java-functional-programming within those boundaries when immutable transformations and composition improve clarity.
  • Relational persistence: Prefer @311-frameworks-spring-jdbc plus @704-technologies-sql. Use @312-frameworks-spring-data-jdbc only when repository-style aggregate access provides a clear benefit.
  • API contracts: Apply @701-technologies-openapi for contract quality and @302-frameworks-spring-boot-rest for Spring runtime implementation.
  • MongoDB: Apply @705-technologies-nosql-mongodb for modeling and query decisions, then @315-frameworks-spring-mongodb for Spring integration.
  • MongoDB migrations: Apply @316-frameworks-spring-mongodb-migrations-mongock when MongoDB changes require versioned data migrations or repeatable migration verification.
  • Modular monoliths: Apply @305-frameworks-spring-boot-modulith when package boundaries, module dependencies, Spring Modulith verification, domain events, or module documentation are in scope.
  • New Spring Boot services: Apply @300-frameworks-spring-boot-create-project when bootstrapping a new Maven-based Spring Boot service or demo module.
  • Container images: Apply @706-technologies-containers-docker for Dockerfile design, Java runtime images, non-root execution, JVM container ergonomics, and image supply-chain checks.

Read the full file on GitHub · 99 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 99 lines · 48 tokens per session scan A 2a5833c8de56

Subscribe to this mod's changes

plinth-java-spring-boot-coder is an agent published in the GitHub repository jabrena/plinth (435 stars, last pushed today), licensed Apache-2.0. It adds 48 tokens to every session and 1,925 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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