Google's pkg.go.dev API reaches v1 with eight JSON endpoints aimed at coding agents

The call is a plain GET with the version in the path. Running `curl https://pkg.go.dev/v1/package/github.com/rshade/ax-go` returns JSON with the module path, the latest version and the package synopsis ^[7]. Symbols and versions sit behind their own endpoints ^[7]. All eight endpoints are stateless ^[2]. A client holds no session, so each lookup fits in a single agent tool call.

That example comes from a dev.to post by the author of ax-go, a library that gives Go CLIs a `__schema` command returning their commands, flags and types as JSON ^[9]. For years before June, a program that wanted package facts had to scrape pkg.go.dev's HTML and hope the markup held ^[1][2]. The part I would build on is the `/v1/` prefix. The API comes with an OpenAPI spec ^[3] and has moved from v1beta to v1 ^[4]. Its reference client, pkgsite-cli, is a Go command-line tool over the JSON API ^[3][8]. The post points out that this is the shape ax-go standardizes, and declines to call it a coincidence ^[8].

Google states the intended consumer outright. "LLMs and agents need precise context. This API provides the data required for agents and models to reason deterministically about Go packages," the announcement says, as quoted in the post ^[6]. The first sentence is right. The second is a claim about the model, and an endpoint controls only what it returns. Version 1 guarantees typed fields from a published contract. Whether a model reasons deterministically over those fields depends on the model.

The post ties the API to Go 1.27, which shipped in August ^[10]. `go test` now runs the `stdversion` vet check by default, flagging uses of standard library symbols newer than the module's `go` directive ^[12]. "Humans rarely make that mistake. Models trained on newer code make it constantly," the author wrote ^[13]. `go fix` gained four more modernizers, which apply mechanical migrations deterministically ^[15]. The author also notes that the 1.27 release notes never use the word "agent" ^[14].

The same post documents what breaks on the tool side once agents read the schema. The trouble on ax-go v0.6.0 was in what finfocus, the author's FinOps CLI, advertised through `__schema --as=mcp` ^[16]. Dispatch is serialized, so one call to a blocking command stalls every call queued behind it ^[17]. The only lever was `Hidden`, and it was the wrong one: it pruned the whole subtree and dropped the command from `--help` for humans as well ^[18]. Version 0.7.0, released September 24, skips command groups and `help` automatically and adds `mcp.Exclude(cmd)` to mark one command as not-a-tool ^[19][20].

For a Go CLI that looks up module versions or importers, I'd move to the v1 endpoints now. Before calling them from an agent's inner loop, I'd want the rate limits, and the post does not cover them.