@Tool annotation
A tool annotation is metadata attached to a method or tool definition that marks it as invocable and describes its operation and characteristics to clients or AI systems.
Spring AI in Action
The @Tool annotation marks a method as a callable tool that an AI application can expose to a language model.
- How it is used
- Exposes Spring-managed Java methods so language models can request real-time data, repository queries, or external capabilities.
- How deep it goes
- Explains annotation metadata, parameter descriptions, registration points, invocation flow, and method security without detailing framework internals.
- Examples
- Uses time-zone lookup, board-game complexity queries, prompt registration, MCP exposure, and secured premium-user access.
- What you can do after
- Build callable Spring AI tools from annotated Java methods and register or secure them for model-driven application requests.
Software Testing with Generative AI
A LangChain4j annotation that marks a method as an invocable tool and supplies natural-language metadata describing its operation.
- How it is used
- Marks methods as LLM-callable tools and describes when their operations match user instructions.
- How deep it goes
- Explains annotation-based method matching, parameter extraction, registration, and execution, but does not detail model decision internals.
- Examples
- Demonstrates room creation, booking creation, database display, and a combined prompt requesting all three operations.
- What you can do after
- Apply it via LangChain4j to expose Java methods that an LLM can select and invoke from natural-language prompts.
Read how Software Testing with Generative AI explains @Tool annotation →
Related concepts
- toolproduces · A tool is an instrument or software capability that enables a person or system to perform a task, obtain information, or interact with resources.
- language modelconfigures · A language model is a computational model that represents patterns in linguistic tokens to estimate sequence probabilities and predict or generate language from context.
- tool usageconfigures · Tool use is an AI system's invocation of external software functions, services, or other capabilities to obtain information or perform actions.
- parameter annotationused by · A LangChain4j annotation that supplies natural-language context for a tool method parameter so a language model can extract its value from a prompt.
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