Lists multiple specific concrete types (Option, Result, Either, Future, IO, Task, State) and concrete use cases (type-safe nullable values, error handling, functional composition with pipeline sub-packages). Very specific about the library and its capabilities.

Clearly answers 'what' (monadic types for Golang using samber/mo with specific type listings and use cases) and 'when' with an explicit 'Apply when...' clause covering three distinct trigger scenarios: using/adopting samber/mo, codebase importing the library, or considering functional programming patterns for Go.

Includes excellent natural trigger terms: 'samber/mo', 'Golang', 'Option', 'Result', 'Either', 'Future', the full import path 'github.com/samber/mo', 'functional programming patterns', 'monadic types', 'nullable values', 'error handling'. These cover both library-specific and conceptual terms a user would naturally use.

Highly distinctive — targets a specific Go library (samber/mo) with a clear niche in functional programming monadic types. The combination of the library name, import path, and specific type names makes it very unlikely to conflict with other skills.

Generally efficient with good code examples and tables, but includes some unnecessary explanations Claude would already know (e.g., 'Inspired by Scala, Rust, and fp-ts', the 'Think of it as...' column comparing to other languages, and the persona/thinking mode preamble). The type comparison table adds marginal value for Claude. Some sections like best practices are well-written but could be tighter.

Excellent executable code examples throughout — Option creation/extraction, Result pipelines with type-changing transforms, Either pattern matching, Do notation, JSON struct tags, database scanning, and pipeline sub-packages. All examples are copy-paste ready with proper imports and realistic use cases.

For a library skill (not a multi-step destructive operation), the workflow is exceptionally clear. The progression from core types → direct methods → sub-package functions → pipes is well-sequenced. The 'Go limitation' callout explaining when to use sub-packages vs direct methods is a critical decision point clearly articulated. The rule of thumb provides clear guidance for choosing between approaches.

References to separate files (option.md, result.md, either.md, pipelines.md, advanced-types.md, monads-guide.md) are well-signaled and one level deep, which is good structure. However, no bundle files were provided, so these references cannot be verified. The main SKILL.md itself is quite long (~200+ lines) and some content (like the full common patterns section) could arguably be in a reference file. Cross-references to other skills are a nice touch.