modelsdotdev-go

A Go client for the models.dev catalog — a community registry of LLM providers and models with their capabilities, token limits, and pricing.

Typed structs over https://models.dev/api.json, an in-memory catalog with lookup/filter helpers, and an HTTP client with TTL caching.

import "github.com/promptrails/modelsdotdev-go"

model, _ := modelsdev.GetModelByID(ctx, "anthropic:claude-opus-4-8")
fmt.Println(model.Name, *model.Cost.Input) // Claude Opus 4.8 5

provider, _ := modelsdev.GetProviderByName(ctx, "OpenAI")
for id := range provider.Models {
    fmt.Println(id)
}

Install

go get github.com/promptrails/modelsdotdev-go

Requires Go 1.26+. No third-party dependencies — standard library only.

Usage

Package-level helpers

Backed by a shared client (live fetch, 1h cache):

model, err := modelsdev.GetModelByID(ctx, "openai:gpt-4o")
provider, err := modelsdev.GetProviderByName(ctx, "Anthropic")

A configured client

c := modelsdev.New(
    modelsdev.WithTTL(30*time.Minute),
    modelsdev.WithUserAgent("my-app/1.0"),
)

cat, err := c.Catalog(ctx) // fetched once, then cached until the TTL expires

// Every reasoning-capable model that also reports a cache-read price:
for _, m := range cat.Filter(func(m modelsdev.Model) bool {
    return m.Reasoning && m.Cost.CacheRead != nil
}) {
    fmt.Printf("%s:%s\n", m.Provider, m.ID)
}

Catalog serves the last good snapshot if a refetch fails. Refresh forces a refetch.

Bring your own snapshot

The library does not ship a baked-in copy of the catalog — it would be stale the moment it's built. If you need catalog data without a network call, fetch a snapshot on your own schedule and parse it:

//go:embed models.json
var snapshot []byte

cat, err := modelsdev.Parse(snapshot)

Catalog API

Method	Returns
Provider(id)	a provider by ID ("openai")
ProviderByName(name)	a provider by display name, case-insensitive ("OpenAI")
Model("provider:model")	a model by fully qualified ID
ModelOf(provider, model)	a model by provider ID + model ID
ProviderIDs()	all provider IDs, sorted
Models()	every model, sorted by provider then model ID
Filter(func(Model) bool)	every model matching a predicate

Missing lookups return ErrNotFound; a malformed qualified ID returns ErrInvalidID.

Data model

Each Model carries its capabilities (Reasoning, ToolCall, Attachment, StructuredOutput, Modalities), Limit (context/output tokens), and Cost (per-1M-token Input, Output, CacheRead, CacheWrite, Reasoning, audio, and long-context tiers). Cost fields are pointers: nil means "not reported", which is distinct from a reported zero.

License

MIT — see LICENSE.