Tango Rust SDK

Official, async-first Rust SDK for the Tango API — federal contracts, IDVs, entities, opportunities, grants, vehicles, and more, with dynamic response shaping so you fetch only the fields you need.

In development — v0.1.0. Not yet at sibling-SDK parity. The public API may shift before v1.0.0. Pin to a specific tag if you depend on this in production.

Sibling SDKs (tango-node, tango-python) are at v1.0.0; tango-go is at v0.1.0 with the same surface. This Rust port ships the full transport, error model, retry / rate-limit handling, webhook signing (in the separate tango-webhooks crate), and the ~75-method API surface. Same 0.x → 1.0 graduation logic as Go: the transport and types are stable; the surface stabilizes once it matches sibling parity.

Features

• Async-first — built on tokio + reqwest. One runtime, clean futures::Stream-based pagination.
• Dynamic response shaping — request exactly the fields you need via 21 built-in SHAPE_* presets or a custom comma-separated field list.
• Typed errors — single Error enum with rich payload variants (Auth, NotFound, Validation, RateLimit, Timeout, Api, Transport, Decode, Build). Programmatic dispatch via err.status() and err.is_retryable().
• Smart retries — automatic backoff on 5xx / 408 / 429 / transport errors, honoring the server's Retry-After header.
• Compile-time-checked client builder — via bon. Missing api_key? Won't compile.
• Async pagination — PageStream<T> implements futures::Stream. Yields one item at a time, fetches successive pages automatically.
• Forward-compatible models — every typed model carries #[serde(flatten)] extra: HashMap<String, Value> so a server-side schema addition surfaces in record.extra["new_field"] rather than being silently dropped.
• Webhook signing — in the separate makegov-tango-webhooks crate: zero transport deps, HMAC-SHA256 verification, constant-time via subtle.

Installation

[dependencies]
makegov-tango = "0.1"

# Optional: webhook signing for receivers
makegov-tango-webhooks = "0.1"

Crates publish under the makegov- prefix on crates.io; Rust imports stay short — use tango::Client; and use tango_webhooks::verify; — thanks to a [lib] name shim in each crate (same pattern as the aws-sdk-* family).

Requires Rust 1.80 or later.

Quick start

use tango::Client;
use futures::TryStreamExt;

#[tokio::main]
async fn main() -> tango::Result<()> {
    let client = Client::builder().api_key("your-api-key").build()?;

    // Single page
    let page = client.list_contracts(
        tango::ListContractsOptions::builder()
            .awarding_agency("9700")
            .shape(tango::SHAPE_CONTRACTS_MINIMAL)
            .limit(25u32)
            .build(),
    ).await?;
    for record in page.results {
        println!("{:?}", record.get("piid"));
    }

    // Walk every page as a stream
    let mut stream = client.iterate_contracts(
        tango::ListContractsOptions::builder()
            .awarding_agency("9700")
            .fiscal_year("2025")
            .build(),
    );
    while let Some(record) = stream.try_next().await? {
        println!("{:?}", record.get("piid"));
    }

    Ok(())
}

Get a typed agency

get_agency returns the typed AgencyRecord; forward-compatible fields land in agency.extra.

# use tango::Client;
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
let agency = client.get_agency("9700", None).await?;
println!("{}", agency.name.unwrap_or_default());
# Ok(()) }

Get a fully-shaped entity

# use tango::{Client, GetEntityOptions, SHAPE_ENTITIES_COMPREHENSIVE};
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
let entity = client.get_entity(
    "ABC123DEF456",
    Some(GetEntityOptions::builder().shape(SHAPE_ENTITIES_COMPREHENSIVE).build()),
).await?;
# Ok(()) }

Authentication

Pass an API key via Client::builder().api_key(...), or set TANGO_API_KEY in the environment and call Client::from_env(). You can also override the base URL via TANGO_BASE_URL for staging environments, or via the builder:

# use tango::Client;
# async fn run() -> tango::Result<()> {
let client = Client::builder()
    .api_key("your-key")
    .base_url("https://staging.tango.makegov.com".to_string())
    .build()?;
# Ok(()) }

Core concepts

Dynamic response shaping

Every list and get endpoint accepts a shape parameter selecting which fields the API returns. The SDK ships 21 presets matching the Node, Python, and Go SDKs:

# use tango::{Client, ListContractsOptions, SHAPE_CONTRACTS_MINIMAL};
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
// Preset:
let page = client.list_contracts(
    ListContractsOptions::builder().shape(SHAPE_CONTRACTS_MINIMAL).build(),
).await?;

// Custom:
let page = client.list_contracts(
    ListContractsOptions::builder()
        .shape("key,piid,recipient(uei,display_name)")
        .build(),
).await?;
# Ok(()) }

See docs/SHAPES.md for the full grammar and the available presets.

Pagination

List endpoints support both page-based and cursor-based pagination. Page<T> exposes the next URL plus the extracted cursor for keyset endpoints:

# use tango::{Client, ListIDVsOptions};
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
let page = client.list_idvs(ListIDVsOptions::builder().limit(50u32).build()).await?;
// Fetch the next page:
let next_page = client.list_idvs(
    ListIDVsOptions::builder().limit(50u32).cursor(page.cursor.unwrap_or_default()).build()
).await?;
# Ok(()) }

Or just iterate via PageStream<T>:

# use tango::{Client, ListIDVsOptions};
# use futures::TryStreamExt;
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
let mut stream = client.iterate_idvs(ListIDVsOptions::builder().build());
while let Some(idv) = stream.try_next().await? {
    // process one IDV at a time
    let _ = idv;
}
# Ok(()) }

Or drain the whole thing:

# use tango::{Client, ListIDVsOptions};
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
let all = client.iterate_idvs(ListIDVsOptions::builder().build()).collect_all().await?;
# Ok(()) }

Rate limits

After each request, client.rate_limit_info() returns a snapshot of the rate-limit headers:

# use tango::Client;
# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
if let Some(info) = client.rate_limit_info() {
    println!(
        "remaining={:?} limit={:?} reset_in={:?}",
        info.remaining, info.limit, info.reset_in
    );
}
# Ok(()) }

The client also automatically retries 429s, honoring Retry-After. See docs/CLIENT.md for the full retry semantics.

Webhook verification

Webhook signing lives in the separate makegov-tango-webhooks crate so a receiver service doesn't have to pull in the full SDK:

use tango_webhooks::{verify, SIGNATURE_HEADER};

fn check(raw_body: &[u8], header_value: &str, secret: &str) -> bool {
    verify(raw_body, header_value, secret)
}

The CRUD methods for managing webhook endpoints and alerts live on tango::Client: list_webhook_endpoints, create_webhook_endpoint, update_webhook_endpoint, delete_webhook_endpoint, test_webhook_endpoint, list_webhook_alerts, create_webhook_alert, etc.

See docs/WEBHOOKS.md for the full surface, signature format, and middleware patterns.

Error handling

Every fallible call returns Result<T, tango::Error>. The Error enum carries rich payloads — match the variant to dispatch on the failure mode:

use tango::{Client, Error};

# async fn run() -> tango::Result<()> {
# let client = Client::builder().api_key("x").build()?;
match client.get_agency("9700", None).await {
    Ok(agency) => println!("{}", agency.name.unwrap_or_default()),
    Err(Error::NotFound { .. }) => println!("not found"),
    Err(Error::RateLimit { retry_after, limit_type, .. }) => {
        println!("rate limited; retry in {retry_after}s (bucket: {limit_type:?})");
    }
    Err(Error::Validation { message, .. }) => eprintln!("bad input: {message}"),
    Err(Error::Api { status, message, .. }) => eprintln!("status={status}: {message}"),
    Err(e) => return Err(e),
}
# Ok(()) }

err.is_retryable() reports the SDK's retry decision (it already retries internally; this is for callers building their own retry policies on top). err.status() returns the HTTP status when one is associated with the error.

API methods

The SDK exposes ~75 methods on Client covering every endpoint in the sibling SDKs. The most-used 15 are listed here; the full method-by-method reference lives in docs/API_REFERENCE.md.

Sub-resources and lookups: list_entity_contracts / _idvs / _otas / _otidvs / _subawards / _lcats / get_entity_metrics, list_idv_awards / _child_idvs / _transactions / _lcats, list_agency_awarding_contracts / _funding_contracts, list_vehicle_awardees / _orders, list_otidv_awards, list_gsa_elibrary_contracts, list_business_types, list_offices, list_departments, list_mas_sins, list_assistance_listings, list_lcats (dispatcher). Meta: resolve, validate, get_version, list_api_keys, search_opportunity_attachments. Metrics dispatcher: list_metrics.

See docs/API_REFERENCE.md for full signatures, filter fields, and quirks.

Workspace layout

This is a Cargo workspace with two published crates:

.
├── crates/
│   ├── tango/             # main SDK
│   └── tango-webhooks/    # HMAC-SHA256 signing/verification (no transport deps)
├── docs/                  # in-repo guides
├── justfile               # task runner (test / fmt / lint / cover / release-check)
├── Cargo.toml             # workspace manifest
└── README.md

Documentation

In-repo guides:

• docs/ARCHITECTURE.md — crate layout, request lifecycle, design rationale
• docs/CLIENT.md — builder options, env vars, retry semantics, error model, rate-limit observability
• docs/API_REFERENCE.md — method-by-method reference for every public method
• docs/SHAPES.md — shape grammar, the 21 presets, flat / flat_lists, trade-offs
• docs/WEBHOOKS.md — receiving deliveries, CRUD methods, troubleshooting

External:

• API docs (Rust): https://docs.rs/makegov-tango · https://docs.rs/makegov-tango-webhooks
• API reference: https://docs.makegov.com
• Sibling SDKs: @makegov/tango-node · tango-python · tango-go

Development

just test         # cargo test --workspace
just fmt          # cargo fmt --all
just lint         # cargo clippy --workspace --all-features -- -D warnings
just cover        # cargo llvm-cov --workspace --lcov --output-path lcov.info
just ci           # fmt-check + lint + test (run before opening a PR)
just release-check  # cargo publish --dry-run for both crates

Requirements

• Rust 1.80 or later.

License

MIT — see LICENSE.

Support

Open an issue at https://github.com/makegov/tango-rust/issues or email support@makegov.com.

Contributing

PRs welcome. See CONTRIBUTING.md. Run just ci before opening — fmt, clippy, and the full test suite must pass.