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/AGENTS.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/instructions/ionide/tree-sitter-fsharp/agents-md)<a href="https://agentmods.dev/instructions/ionide/tree-sitter-fsharp/agents-md"><img src="https://agentmods.dev/badge/instructions/ionide/tree-sitter-fsharp/agents-md/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/instructions/ionide/tree-sitter-fsharp/agents-md"><img src="https://agentmods.dev/badge/instructions/ionide/tree-sitter-fsharp/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.03741 | $0.03741 |
| Opus 5.5 | $0.01496 | $0.01496 |
| Sonnet 5.5 | $0.00748 | $0.00748 |
| Haiku 4.5 | $0.00374 | $0.00374 |
Grade A, and why
tree-sitter-fsharp AGENTS.md 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 1mo 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 — 319 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Improving the F# Tree-sitter Parser
This document explains how to add new language features to the F# parser.
Project Structure
This project contains two parsers:
fsharp/- Parses.fsand.fsxfiles (F# source and script files)fsharp_signature/- Parses.fsifiles (F# signature files)
These are not independent. fsharp_signature/grammar.js starts with
grammar(require("../fsharp/grammar"), { ... }) — it extends the base
grammar and overrides/adds a small number of rules. Consequences you must
internalize:
- A change to
fsharp/grammar.jschanges the derived signature grammar too, even if you never openfsharp_signature/grammar.js. - Both
fsharp/src/parser.candfsharp_signature/src/parser.cmust be regenerated after any change tofsharp/grammar.js. Forgetting the second one will fail CI's "parser matches grammar" check. - Use
npm run generate(regenerates both) rather than a singletree-sitter generateinvocation — see the workflow section below.
Each parser directory contains:
grammar.js- The grammar definition (written in JavaScript)src/grammar.json- Generated grammar in JSON formatsrc/parser.c- Generated C parser code (never edit this file directly)src/scanner.c- Thin per-parser shim that#includes the shared scanner
The real external scanner logic lives in a single shared header at
common/scanner.h. Both fsharp/src/scanner.c and
fsharp_signature/src/scanner.c are just three-function shims that delegate
to functions defined in that header. If you need to change tokenization
behavior (indent/dedent, keyword handling, string interpolation, etc.),
edit common/scanner.h — never the per-parser scanner.c shim.
Running the CLI
The tree-sitter CLI is installed as a local devDependency
(node_modules/.bin/tree-sitter), not globally. Invoke it with
npx tree-sitter <command>, which resolves the local binary
automatically. All examples in this document use npx tree-sitter ....
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.
- 1mo ago Changed · +82 lines · +1,277 tokens per session dfbe128fbd5d
- 2mo ago First seen · 237 lines · 2,464 tokens per session scan A c342f79e5d8c
tree-sitter-fsharp AGENTS.md is an instructions file published in the GitHub repository ionide/tree-sitter-fsharp (98 stars, last pushed 16d ago), licensed MIT. It adds 3,741 tokens to every session, about $0.0150 per session on Opus 5.5. 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 instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.