What is js-bson AGENTS.md?

Repository instructions for BSON, a JavaScript library that converts data to and from BSON, a binary document format used by MongoDB. It supports Node.js and web browsers.

Building bundles and type declarations, checking code and public APIs, running Node.js or browser tests, running one test file, and measuring performance with benchmarks.

They identify the source of truth and list the build, lint, formatting, browser, Node.js, and type-check commands, so changes can be validated consistently.

How mongodb/js-bson configures Codex and OpenCode

About the project

mongodb/js-bson is a library that parses BSON, a binary format for JSON-like documents, in Node.js and web browsers. It serves applications that need to read or work with BSON data.

mongodb/js-bson · 1,216 stars · on GitHub

Reuse

Borrowing it

Nothing to install: this file belongs to mongodb/js-bson. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/mongodb/js-bson/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/mongodb/js-bson

Made for: Codex, OpenCode.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/mongodb/js-bson/agents-md/github.svg)](https://agentmods.dev/instructions/mongodb/js-bson/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/mongodb/js-bson/agents-md"><img src="https://agentmods.dev/badge/instructions/mongodb/js-bson/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/mongodb/js-bson/agents-md"><img src="https://agentmods.dev/badge/instructions/mongodb/js-bson/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,397 This file is loaded in full into every session.

When invoked 1,397 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.01397	$0.01397
Opus 5.5	$0.00559	$0.00559
Sonnet 5.5	$0.00279	$0.00279
Haiku 4.5	$0.00140	$0.00140

Measured 2mo ago against content hash 4b9b7174ae24, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

js-bson 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 2mo 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.

AGENTS.md · 80 lines

How it starts

The opening of the file, as written. The whole thing — 80 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

Instructions for AI coding agents working in this repository. This file is the source of truth; tool-specific files (e.g. CLAUDE.md) should only import it.

Project Overview

bson is the BSON codec library for JavaScript (Node.js and browser), implementing the BSON specification. It provides BSON type classes, serialization/deserialization to and from BSON bytes, and Extended JSON (EJSON) support. It is the codec used by the node-mongodb-native driver, and also a standalone library external users depend on.

Commands

npm run build          # tsc + api-extractor (bson.d.ts) + rollup bundles into lib/
npm run check:lint     # eslint + api-extractor + tsd type tests
npm run format         # attempts to automatically fix lint errors
npm run check:node     # mocha test/node (Node target). Run `build` first
npm run check:web      # same suite with WEB=true (browser code paths)
npm test               # builds (pretest), then check:node + check:web

Run a single test file: npx mocha test/node/<file>.test.ts; filter cases with --grep.
Tests use mocha + chai + sinon. Type-level tests live in test/types (tsd).

Benchmarks

All benchmark runs first measure a CPU baseline (check:baseline-bench) so results are normalized across machines. Sources live in test/bench/.

npm run check:granular-bench   # per-BSON-type micro-benchmarks (test/bench/granular)
npm run check:spec-bench       # cross-driver spec benchmark suite (test/bench/spec)
npm run check:custom-bench     # ad-hoc/scenario benchmarks (test/bench/custom)

Use these to validate perf-tagged changes — run before and after on the same machine and compare.

Structure

src/index.ts — the public API surface. api-extractor rolls it into bson.d.ts.
src/*.ts — BSON type classes (ObjectId, Long, Decimal128, Binary, …), all extending BSONValue; extended_json.ts for EJSON.
src/parser/ — the eager codec: recursive serializer/deserializer that converts whole JS objects to/from BSON bytes in one pass, plus size calculation used to pre-allocate output buffers.
src/parser/on_demand — the lazy path: scans a BSON buffer into document metadata without materializing JS values, so they can be independently decoded.
src/utils/ — shared helpers (byte utils, number parsing, platform detection).
test/node/ — main test suite; bson_corpus* tests run the cross-driver BSON corpus spec.

Read the full file on GitHub · 80 lines

Changes

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.

2mo ago First seen · 80 lines · 1,397 tokens per session scan A 4b9b7174ae24

Subscribe to this mod's changes

js-bson AGENTS.md is an instructions file published in the GitHub repository mongodb/js-bson (1,216 stars, last pushed yesterday), licensed Apache-2.0. It adds 1,397 tokens to every session, about $0.0056 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.

Databases MongoDB bson bson-library node-js nodejs

js-bson AGENTS.md next to 6 instructions from other repositories
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js-bson: Instructions file for Codex