When to use services.

If you want to have a node perform quick computations or do some actions on demand (enabling/disabling a motor, starting/stopping a robot).

at the interface definition, you can see that the request and response are separated by three dashes (---). In the response,

How Create custom service interface

Make srv folder inside my_robot_interfaces package

.
├── CMakeLists.txt
├── msg
├── package.xml
└── **srv**

naming conventions for Service interfaces

• Use UpperCamelCase (PascalCase) for naming—for example, ActivateMotor.
• Avoid adding "Srv" or "Interface" to the name as it creates unnecessary redundancy.
• Always use the .srv file extension.
• Include a verb in the interface name (e.g., TriggerSomething, ActivateMotor, ComputeDistance). Since services perform actions or computations, using a verb clearly indicates the service's purpose.

create interface file

All the fields inside the definition must follow the snake_case convention (use underscores between words, all letters lowercase, and no space).

int64 reset_value
---
bool success
string message

Build the interface

• update rosidl_generate_interfaces() function function of CmakeLists