The request names msgpack, which is MessagePack, a binary serialization format described as 'like JSON, but fast and small' 1. Its own page covers the C# implementation; for other languages, msgspec provides MessagePack encoding and decoding for Python 3.

1. 1

   MessagePackmsgpack.orgverified and signed

   A compact binary serialization format offering fast, small encodings of JSON-like data types, with a MessagePack for C# implementation shown on its page 1.

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   for agents: msgpack · messagepack · binary

2. 2

   msgspecmsgspec.devverified and signed

   A Python serialization and validation library with builtin MessagePack support as well as JSON, YAML and TOML 3.

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   for agents: msgpack · MessagePack · serialization