# Agent-First Data for Go
```bash
go get github.com/agentfirstkit/agent-first-data/go
```
```go
package main
import (
"fmt"
afdata "github.com/agentfirstkit/agent-first-data/go"
)
func main() {
event, _ := afdata.NewJSONResult(map[string]any{
"api_key_secret": "sk-123",
"latency_ms": 1280,
"db_url": "postgres://user:p@ss@db/app?token_secret=abc",
}).Build()
value := event.Value()
fmt.Println(afdata.OutputJson(value))
fmt.Println(afdata.OutputPlain(value))
}
```
Useful names use Go casing: `OutputJson`, `OutputYaml`, `OutputPlain`, `OutputJsonWithOptions`, `OutputOptionsForPolicy`, `RedactedValue`, `RedactURLSecrets`, `RedactArgv`, `NormalizeUTCOffset`, `IsValidRFC3339Date`, `IsValidRFC3339Time`, `IsValidRFC3339`, `IsValidBCP47`, `CliParseOutput`, `CliOutput`, `BuildCliError`, `BuildCliVersion`, `CliHandleVersionOrContinue`, and `DecodeProtocolEvent`.
Scoped redaction and extra secret names use the `Redactor` struct:
```go
r := afdata.Redactor{SecretNames: []string{"authorization"}}
fmt.Println(afdata.OutputJson(r.Value(value)))
fmt.Println(r.URL("https://api.example.com/?authorization=abc"))
```
## Behavior Notes
- Default redaction replaces every `_secret` or configured secret-name subtree with `***`, including objects and arrays.
- `_url` fields scrub userinfo passwords and secret-named query parameters; surrounding whitespace is trimmed and internal whitespace redacts the whole field.
- YAML keeps original keys and values (structure-preserving, like JSON), sorting keys by UTF-16 code unit order and quoting/escaping unsafe keys and string scalars. Plain strips formatting suffixes, formats values, sorts the same way, and renders nested objects/arrays as canonical JSON.
- Logging records use `kind:"log"` with a nested `log` payload and a separate `level` field, so error-level logs are not terminal protocol errors.
- `build_cli_error(message, hint?)` returns a strict-ready CLI error with `error.retryable:false` and `trace:{}`.
- Use `CliHandleVersionOrContinue()` before argument parsing so `--version` always answers with a structured protocol-v1 `kind:"result"` version event. An explicit `--output` wins; pass the command's normal output as the optional final argument (JSON when omitted), plus its value-taking global flag names.
## Reference
- Formal cross-language contract: [spec/agent-first-data.md](https://github.com/agentfirstkit/agent-first-data/blob/main/spec/agent-first-data.md)
- Conformance fixtures: [spec/fixtures](https://github.com/agentfirstkit/agent-first-data/tree/main/spec/fixtures)
- Agent skill: [skills/agent-first-data/SKILL.md](https://github.com/agentfirstkit/agent-first-data/blob/main/skills/agent-first-data/SKILL.md)