Borrowing it
Nothing to install: this file belongs to ionide/tree-sitter-fsharp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/ionide/tree-sitter-fsharp/main/.opencode/skills/tree-sitter-tdd/SKILL.mdgit clone --depth 1 https://github.com/ionide/tree-sitter-fsharpWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ionide/tree-sitter-fsharp/tree-sitter-tdd)<a href="https://agentmods.dev/skills/ionide/tree-sitter-fsharp/tree-sitter-tdd"><img src="https://agentmods.dev/badge/skills/ionide/tree-sitter-fsharp/tree-sitter-tdd/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ionide/tree-sitter-fsharp/tree-sitter-tdd"><img src="https://agentmods.dev/badge/skills/ionide/tree-sitter-fsharp/tree-sitter-tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 12 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium MCP Rug Pull · line 38 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 39 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 148 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 160 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 177 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 191 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 218 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 227 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 329 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 330 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 331 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 332 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
What 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 5.1 | $0.00025 | $0.02703 |
| Opus 5 | $0.00013 | $0.01352 |
| Sonnet 5 | $0.00005 | $0.00541 |
| Haiku 4.5 | $0.00003 | $0.00270 |
Grade A, and why
tree-sitter-tdd 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 9d 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 — 339 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tree-Sitter TDD Skill
Overview
Use this skill when adding a new F# language feature to the tree-sitter parser. This skill automates the TDD workflow: write test first, get Fantomas AST, map to tree-sitter format, verify with user, and then strictly orchestrate multi-agent iteration—spawning per-test subagents for parse fixes until all test cases pass. Full green suite is mandatory.
Critical: This workflow loops—using delegated subagents—until ALL tests pass. Adding a feature may break existing tests; every breakage is isolated and fixed before success is declared.
When to Use
- Adding a new language feature (e.g., new expression type, pattern, keyword)
- Fixing a parsing issue with existing syntax
Prerequisite
- The script
ast_parser.fsxat project root must accept the code example as a command-line argument. If it does not, update the script before continuing. See Step 1 for the exact required change.
Input
The user provides:
- F# code snippet to parse
- Test name (e.g., "nullable type")
- Corpus file (e.g.,
test/corpus/type_defn.txt)
Workflow
Multi-Agent Orchestration Pattern
After a new test is written and (expectedly) fails, use the following orchestration:
- Spawn a subagent (with the
tree-sitter-parse-testingskill) to iterate on parser and grammar only for the failing example until it parses as required.- IMPORTANT: The subagent must focus on fixing that single test case. The subagent should never call
npx tree-sitter testor attempt to fix multiple cases. It is strictly one subagent per failing test.
- IMPORTANT: The subagent must focus on fixing that single test case. The subagent should never call
- Once that test parses, run the entire test suite (
npx tree-sitter test). - For every other test that fails, spawn a new subagent, each focusing solely on its failing case.
- Continue this loop, always re-running and spawning as needed, until all tests pass.
- Never “fix everything at once”; maintain one-failure-at-a-time discipline per subagent.
This coordination ensures robust TDD and protects against missed breakages elsewhere in the corpus. (See Step 7 for concrete mechanics.)
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.
- 9d ago First seen · 339 lines · 25 tokens per session scan A 9fdce3ca40c5
tree-sitter-tdd is a skill published in the GitHub repository ionide/tree-sitter-fsharp (96 stars, last pushed 6d ago), licensed MIT. It adds 25 tokens to every session and 2,703 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 2026-08-30.
Other skills, from other repositories
typescript-test-writing
Use this skill when writing or modifying tests in the llxprt-code repository. Covers mandatory TDD, behavioral testing, bun:test conventions and file naming, mock hygiene (no mock theater), and what never to test. Distilled from dev-docs/RULES.md, which remains the source of truth.
nw-fp-clojure
Clojure language-specific patterns, data-first modeling, REPL-driven development, and spec.
nw-fp-fsharp
F# language-specific patterns, Railway-Oriented Programming, and Computation Expressions.
python
Python development with ruff, mypy, pytest - TDD and type safety.
golang-testing
A guide to testing Go programs, including test-driven development (TDD), table-driven tests, coverage, and debugging. TDD means writing a failing test before implementing the code that makes it pass.
python-testing
A Python testing guide covering pytest, test coverage, and test-driven development (TDD), a method of writing a failing test before the code that makes it pass.