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 skills/huggingface/openenv/write-testsnpx skills add huggingface/OpenEnv --skill write-testsgit clone --depth 1 https://github.com/huggingface/OpenEnvWhat 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 | $0.00017 | $0.00487 |
| Opus 5 | $0.00009 | $0.00244 |
| Sonnet 5 | $0.00003 | $0.00097 |
| Haiku 4.5 | $0.00002 | $0.00049 |
Grade A, and why
write-tests 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 yesterday.
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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
/write-tests
Write failing tests that encode acceptance criteria.
Usage
/write-tests
/write-tests Add logout button to header
When to Use
- After creating a todo that requires implementation
- Before running
/implement - When you have clear acceptance criteria
When NOT to Use
- Implementation already exists (tests would pass immediately)
- You're exploring or prototyping (not TDD mode)
- Just adding to existing test coverage
What It Does
- Analyzes the current todo/requirement
- Reads existing tests to understand patterns
- Writes test files that verify acceptance criteria
- Verifies tests FAIL (proves they test something real)
- Returns test file paths for
/implement
Output
The tester agent will produce:
## Tests Written
### Files Created/Modified
- `tests/test_client.py`
### Tests Added
| Test | Verifies |
|------|----------|
| `test_client_reset_returns_observation` | Reset returns valid observation |
| `test_client_step_advances_state` | Step mutates state correctly |
| `test_client_handles_invalid_action` | Error handling for bad input |
### Verification
All tests FAIL as expected (no implementation yet).
### Next Step
Run `/implement` to make these tests pass.
Rules
- Read existing tests first to understand patterns and conventions
- Test behavior, not implementation - write from user's perspective
- Integration tests first, then unit tests if needed
- Each test verifies ONE thing clearly
- Run tests to verify they fail before returning
Anti-patterns (NEVER do these)
- Writing tests that pass without implementation
- Testing implementation details instead of behavior
- Writing overly complex test setups
- Adding implementation code (that's
/implement's job) - Writing tests that duplicate existing coverage
Completion Criteria
Before returning, verify:
- Tests compile/run successfully (pytest can collect them)
- Tests FAIL (no implementation yet)
- Test names clearly describe what they verify
- Tests follow existing project patterns (see
tests/for examples)
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.
- yesterday First seen · 86 lines · 17 tokens per session scan A e5904765dff7
write-tests is a skill published in the GitHub repository huggingface/OpenEnv (2,531 stars, last pushed 4d ago), licensed BSD-3-Clause. It adds 17 tokens to every session and 487 once invoked, about $0.0001 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 2026-08-31.
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