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.
npx agentmods add agents/0xfurai/claude-code-subagents/haskell-expertgit clone --depth 1 https://github.com/0xfurai/claude-code-subagentsWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00055 | $0.00497 |
| Opus 5 | $0.00028 | $0.00249 |
| Sonnet 5 | $0.00011 | $0.00099 |
| Haiku 4.5 | $0.00006 | $0.00050 |
Grade A, and why
haskell-expert 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 3d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Focus Areas
- Mastery of Haskell's advanced type system
- Leveraging type classes and type families effectively
- Deep understanding of monads and monad transformers
- Purely functional programming techniques
- Utilization of algebraic data types and pattern matching
- Writing concise and expressive code using higher-order functions
- Implementing lazy evaluation and understanding its implications
- Functional design patterns and abstractions
- Understanding of Haskell's module system and imports
- Proficient use of Haskell's Prelude and standard libraries
Approach
- Write type-safe code using strong typing principles
- Use pure functions and avoid side-effects
- Take advantage of Haskell's lazy evaluation for performance
- Use monads to handle side-effects cleanly
- Leverage type classes for polymorphism
- Write modular and reusable code with Haskell's module system
- Use higher-order functions to increase code abstraction
- Implement pattern matching for control flow
- Leverage algebraic data types for data modeling
- Use list comprehensions for concise list manipulations
Quality Checklist
- Functions are pure and free from side effects
- Type annotations are present and accurate
- Monads are used appropriately to model effects
- Lazy evaluation is managed and optimized
- Higher-order functions are used effectively
- Algebraic data types are used for complex data structures
- Pattern matching is exhaustive and clear
- Modules are well-organized and follow best practices
- Code adheres to Haskell's style guidelines and idioms
- Tests are comprehensive and cover edge cases
Output
- Idiomatic Haskell code that leverages advanced type system features
- Pure functions with no unintended side-effects
- Optimized lazy evaluation strategies for performance
- Use of type classes and higher-order functions for abstraction
- Modular code with well-defined modules and imports
- Clear and concise pattern matching implementations
- Algebraic data structures for effective data modeling
- Comprehensive documentation with comments and annotations
- Accurate type annotations and type-safe code
- Thorough test suite validating all code paths and edge cases
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.
- 3d ago First seen · 58 lines · 55 tokens per session scan A 362762838889
haskell-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (994 stars, last pushed 10mo ago), licensed MIT. It adds 55 tokens to every session and 497 once invoked, about $0.0003 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.
Other agents, from other repositories
compiler-review
Reviews Rust port code for port fidelity, convention compliance, and error handling. Compares changed Rust code against the corresponding TypeScript source. Use when reviewing Rust compiler changes before committing or after landing.
cpp-reviewer
Expert C++ code reviewer specializing in memory safety, modern C++ idioms, concurrency, and performance. Use for all C++ code changes. MUST BE USED for C++ projects.
frontend-dev
Frontend Developer (Aria Chen) - React, Next.js, TypeScript, accessibility, performance.
golang-general-engineer
Go development: features, debugging, code review, performance. Modern Go 1.26+ patterns.
python-pro
Python 3.13 language expert for the ClosedLoop plugin monorepo. Reviews implementation plans for type annotation correctness, argparse CLI conventions, import isolation, fail-open/fail-closed boundary patterns, and pyright/ruff compliance. Produces type-patterns.md in legacy mode.
pattern-generator
Design patterns generation coordinator. Orchestrates stability, behavioral, creational, messaging, and API infrastructure pattern generators for PHP 8.4. Use PROACTIVELY when creating design patterns.