| name | capability |
| description | Creates or modifies a capability class in domain/capabilities/ and its corresponding Has* interface in domain/tools/contracts.ts. Use when adding a new tool runtime behavior (agents, skills, commands, rules, mcp, hooks, settings, plugins), changing the constructor params of an existing capability class, or wiring a new capability into an existing AiTool definition. Do NOT use for AI tool definitions — use `tool` instead. Do NOT use for domain value objects or discriminant unions — use `domain-model` instead. Do NOT use for pure string transforms — use `format` instead.
|
Capability
Builds a capability class that encapsulates one tool runtime behavior and its corresponding
Has* interface in domain/tools/contracts.ts. Each capability class is instantiated in
exactly one AiTool<C> file; the Has* interface declares the typed field in the C parameter.
Available actions
| # | Action | Role | Input |
|---|
| 01 | define-has-interface | Declare the Has* interface in domain/tools/contracts.ts | capability name + field type |
| 02 | write-capability-class | Write the capability class in domain/capabilities/ | Has* interface from 01 |
| 03 | wire-into-tool | Add the capability to an AiTool definition | capability class from 02 |
| 04 | test | Write unit tests covering constructor params and public API | completed capability from 02 |
Default flow
01 → 02 → 03 → 04
Skip 01 when the Has* interface already exists in contracts.ts and only the class needs updating.
Skip 03 when the new capability is not yet needed by any existing tool (e.g. adding it speculatively).
Transversal rules
Has* interface lives in domain/tools/contracts.ts; the field type is the capability class.- Capability class file lives in
domain/capabilities/<kebab-name>-capability.ts; one class per file.
- Capability class name ends in
Capability (e.g. WidgetsCapability).
- Constructor accepts a single params object; no positional arguments.
- All public fields are
readonly; no setters.
- Throw
CapabilityConfigError (from domain/errors.ts) on invalid constructor params.
- Capability presence guard uses the
in operator: "widgets" in tool.capabilities — never instanceof.
- Named export only; no default export.
- No
any types.
.js extensions on all relative imports.
References
references/capability-conventions.md — class shape, constructor params object, CapabilityConfigError, readonly fieldsreferences/has-interface.md — Has* interface placement, naming, and capability-presence guard
Invariant rules
references/capability-conventions.md — authoritative capability class rules
