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 instructions/mongodb/js-bson/agents-mdgit clone --depth 1 https://github.com/mongodb/js-bsonWhat 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 | $0.01397 | $0.01397 |
| Opus 5 | $0.00698 | $0.00698 |
| Sonnet 5 | $0.00279 | $0.00279 |
| Haiku 4.5 | $0.00140 | $0.00140 |
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 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 — 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 extendingBSONValue;extended_json.tsfor 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.
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 · 80 lines · 1,397 tokens per session scan A 4b9b7174ae24
js-bson AGENTS.md is an instructions file published in the GitHub repository mongodb/js-bson (1,216 stars, last pushed 4d ago), licensed Apache-2.0. It adds 1,397 tokens to every session, about $0.0070 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 instructions, from other repositories
kerberos AGENTS.md
Instructions for mongodb-js/kerberos, covering agents.md, project overview, commands, structure and code conventions.
zstd AGENTS.md
Instructions for mongodb-js/zstd, covering agents.md, project overview, commands, structure and code conventions.
kerberos CLAUDE.md
Instructions for mongodb-js/kerberos, a project described as: Kerberos library for node.js.
zstd CLAUDE.md
Instructions for mongodb-js/zstd, a project described as: A Zstd Compression Library.
rustwright AGENTS.md
Instructions for Skyvern-AI/rustwright, covering repository instructions, public boundary, pull-request review, local verification and browser launches.
KarmaCircle AGENTS.md
Instructions for karmacircleCommunity/KarmaCircle, covering agentic workflow, git / branching, the apps/web ↔ apps/api boundary, repo-specific guardrails and when you're not sure which duplicate a request means.