Rust

cargo add agent-first-data
# data/protocol surface only — no CLI compiler, emitter, tracing, or skill admin:
cargo add agent-first-data --no-default-features

use agent_first_data::{OutputFormat, OutputOptions, json_result, render};
use serde_json::json;

fn main() {
    let event = json_result(json!({
        "api_key_secret": "sk-123",
        "latency_ms": 1280,
        "db_url": "postgres://user:p@ss@db/app?token_secret=abc"
    }))
    .build();

    let options = OutputOptions::default();
    println!("{}", render(event.as_value(), OutputFormat::Json, &options));
    println!("{}", render(event.as_value(), OutputFormat::Plain, &options));
}

Useful names use Rust casing: render (the single value × format × options → String entry point), OutputFormat, OutputOptions, Redactor, redacted_value, redact_url_secrets, redact_urls_in_text, redact_argv, normalize_utc_offset, is_valid_rfc3339_date, is_valid_rfc3339_time, is_valid_rfc3339, is_valid_bcp47, CliSpec, CommandSpec, ArgSpec, Combination, OutputSpec, SourceSet, SourceScheme, ValueSource, ErrorSpec, lint_value, build_afdata_cli, and decode_protocol_event.

The general-purpose features below are on by default; --no-default-features opts out. Tracing integration is behind tracing: afdata_tracing::AfdataLayer is composable and accepts an injected writer, while try_init is the global-subscriber convenience entry point. The whole CLI surface — CliSpec, help-v2, emitters, and the AFDATA adapter — is behind cli; skill administration is behind skill-admin; stdout/stderr file redirection is behind stream-redirect. Unix hardened document opens are behind libc, which is on by default and is also enabled by stream-redirect. render and OutputFormat stay available with every feature off.

use agent_first_data::afdata_tracing::{self, LogFormat};
use agent_first_data::Redactor;
use tracing_subscriber::EnvFilter;

fn init_logging() -> Result<(), tracing_subscriber::util::TryInitError> {
    afdata_tracing::try_init(
        EnvFilter::new("info"),
        LogFormat::Json,
        Redactor::new().secret_names(["authorization"]),
    )
}

For a closed-world CLI, bind exact action handlers and resolve argv to CliOutcome. The application owns the process lifecycle because a finite command, a long-running event stream, and raw-byte output need different execution and output policies. Use the resolved OutputPlan with CliEmitter::finish, write_raw, and, when enabled, stream_redirect. rust/examples/agent_cli.rs shows the finite-command case.

An ArgSpec can declare indirect values with sources(SourceSet::config()) (env:NAME, file:PATH#DOT_PATH, or file+FORMAT:PATH#DOT_PATH) or SourceSet::stream() (also stdin, fd:N, and prompt). Parse the resolved string with that same set, then call ValueSource::read() for an ordinary value or read_secret() for a credential. The latter returns agent_first_data::value_source::SecretString; its Debug and Display render ***, and only expose_secret() reveals it at the boundary that needs the credential. Host-only schemes are declared with host_scheme and read by the host. Empty strings remain values, reads are capped, and an fd:N read does not close the caller-owned descriptor.

Canonical flags are --stdout-file and --stderr-file. They redirect the corresponding stream to an append-only file; stdout keeps the selected AFDATA output format, and stderr keeps native diagnostics such as panics and backtraces.

Behavior Notes

Reference