Protocol Buffers

You have a `.proto` file. It is the truth for a service, and now somebody outside that service needs the same shape - as JSON Schema for a validation step, as a data contract for a review, as a table for analytics. The usual answer is to retype it. This article replaces the retyping with one HTTP call, and then spends most of its length on the part that matters more: reading what the conversion cost you.

Most schema converters are one-way. You can get *out* of the format or *into* it, rarely both, and the documentation usually leaves you to discover which by trying. So let us answer the direction question for Protocol Buffers first and in one sentence: **proto3 decodes and encodes.** The key `protobuf` (alias `proto`) appears in both the decode list and the encode list, so it is valid as a source and as a target on every route below.

"Take our telemetry `.proto` and give me the Postgres table for it - and tell me what we lose."

A conversion you run once is a favor. A conversion you run on every commit is infrastructure, and infrastructure needs two properties that one-off tooling never has to prove: the second run must produce the same bytes as the first, and when the input changes in a way the conversion cannot honor, the pipeline must stop rather than quietly produce something different.

Proto3 has fifteen scalar types. A neutral intermediate representation that also hosts JSON Schema, SQL, Avro, LinkML, OWL, and half a dozen other formats cannot afford fifteen distinct numeric primitives, and any tool that claims otherwise is hiding something. The arithmetic settles the question up front: some proto3 facts map structurally, some ride alongside as preserved detail, and some are declared as loss. This is the complete account, in that order.