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/microsoft/agents-for-net/serialization-extensiongit clone --depth 1 https://github.com/microsoft/Agents-for-netWhat 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 | $0.00503 | $0.00503 |
| Opus 5 | $0.00251 | $0.00251 |
| Sonnet 5 | $0.00101 | $0.00101 |
| Haiku 4.5 | $0.00050 | $0.00050 |
Grade A, and why
Agents-for-net serialization-extension.instructions.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 2d 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 — 32 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Serialization Extension Context
When working on serialization infrastructure, read docs/serialization-extension-sequence-diagram.md for the full mermaid sequence diagrams covering compile-time generation, runtime initialization, and extension patterns.
Key Design Points
ProtocolJsonSerializeris a static class withSerializationOptions(System.Text.Json) andEntityTypesdictionary. All SDK serialization routes through it.[SerializationInit]marks a class/struct whosepublic static void Init()method will be called whenProtocolJsonSerializeris first accessed (via its static constructor). Use it to register converters viaApplyExtensionConvertersor resolvers viaAddTypeInfoResolver.[EntityName("name")]overrides the key used to register an Entity subclass inEntityTypes. Without it, the class name is used.- Source generators (
SerializationInitSourceGenerator,EntityInitSourceGenerator) emit assembly-level attributes at compile time — no explicit[assembly: ...]lines are authored by developers. - Thread safety — All mutations to
SerializationOptionsuse copy-on-write under_optionsLock. Never mutate the currentSerializationOptionsinstance directly; always go throughApplyExtensionConverters,AddTypeInfoResolver, orApplyExtensionOptions. - Late-loaded assemblies — Both init attributes hook
AppDomain.AssemblyLoadto handle assemblies loaded after the static constructor runs.
Conventions
- Extension libraries place their
[SerializationInit]class in aSerialization/subfolder (e.g.,Microsoft.Agents.Extensions.MSTeams/Serialization/SerializationInit.cs). - The
Init()method must bepublic static void Init()— the runtime invokes it by reflection. - Custom
JsonConverterclasses live underSerialization/Converters/. - Entity subclasses need only inherit from
Entity; theEntityInitSourceGeneratorhandles registration automatically. - When replacing
TypeInfoResolver, always includeCoreJsonContext.Defaultin the chain viaJsonTypeInfoResolver.Combine(...). - Use
System.Text.Jsonexclusively — Newtonsoft.Json is not used in this SDK.
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.
- 2d ago First seen · 32 lines · 503 tokens per session scan A cf74b5ef36ca
Agents-for-net serialization-extension.instructions.md is an instructions file published in the GitHub repository microsoft/Agents-for-net (177 stars, last pushed 4d ago), licensed MIT. It adds 503 tokens to every session, about $0.0025 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
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
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).
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
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 oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.