SDK

# Rust SDK

The `synter` crate on crates.io (0.1.1). An async client (tokio + reqwest) for `POST /api/v1/tools/run`. Every call returns `Result<serde_json::Value, SynterError>`.

## Install and authenticate

bash

```
cargo add synter serde_json
cargo add tokio --features macros,rt-multi-thread
```

rust

```
use synter::{Client, Platform, SynterError};

#[tokio::main]
async fn main() -> Result<(), SynterError> {
    let client = Client::builder()
        .api_key(std::env::var("SYNTER_API_KEY").expect("SYNTER_API_KEY not set"))
        .build()?;

    let campaigns = client.campaigns().list(Default::default()).await?;
    println!("{campaigns}");
    Ok(())
}
```

The client sends `Authorization: Bearer syn_…`.

| Surface | Accepted | Use |
| --- | --- | --- |
| REST tools endpoint | Authorization: Bearer syn_…, X-Synter-Key: syn_…, X-API-Key: syn_… | Authorization: Bearer syn_… |
| REST resource endpoints | Authorization: Bearer syn_…, X-Synter-Key: syn_… | Authorization: Bearer syn_… |
| SDKs (Python, TypeScript, Rust, Java, Go) and the synter CLI | The SDK sets the header for you | Pass the key to the client. Every SDK sends Authorization: Bearer syn_… |
| Local stdio MCP (npm @synterai/mcp-server) | Set SYNTER_API_KEY in the server's env block | The package sends Authorization: Bearer syn_… |
| Hosted MCP | Browser OAuth (the client sends Authorization: Bearer <OAuth access token>), or X-Synter-Key: syn_… for headless clients | OAuth. Headless: X-Synter-Key. Do not put an API key in Authorization on this host. |

Keys start with `syn_` (sandbox keys with `syn_test_`). Create one at [synterai.com/developer](https://synterai.com/developer), keep it in `SYNTER_API_KEY` or a secret store, and send one header per request. On the hosted MCP endpoint, the `Authorization` header is reserved for the OAuth token the client gets from browser sign-in, so a failed key there shows up as a sign-in prompt rather than a key error. Use `X-Synter-Key` when you connect a hosted MCP client with a key. Details: [Authentication](https://docs.synterai.com/api/authentication).

## Write: pause a campaign and change its daily budget

These calls change a live Google Ads campaign. The `Platform` argument is required, but the request always goes to Google Ads; use the REST endpoints for other platforms.

rust

```
use std::collections::HashMap;
use serde_json::json;

let campaign_id = "1234567890";

// Pause (Google Ads)
let paused = client.campaigns().pause(campaign_id, Platform::Google).await?;

// Change the daily budget to 75.00 in the account currency.
// campaigns().update_budget(...) in 0.1.1 sends --budget, which the API rejects
// with 400 UNRECOGNIZED_ARGS before anything runs. Use execute() until the next
// release. Keys are used as flag names verbatim ("daily-budget" -> --daily-budget).
let mut args = HashMap::new();
args.insert("campaign-id".to_string(), json!(campaign_id));
args.insert("daily-budget".to_string(), json!(75.0));
let result = client
    .execute("update_campaign_budget", args, Some("google"))
    .await?;

if result["status"] == "pending_review" {
    println!("Held for approval, nothing ran: {}", result["audit_id"]);
}
```

Writes the safety gate holds or refuses

With the default workspace policy, pausing a campaign and changing a budget run straight away and are recorded in the audit log. Enabling or resuming a campaign, deleting or removing anything, sending creative to a platform, and creating new campaigns can be held for approval. A held write returns HTTP 202 with `status: "pending_review"`, an `audit_id` and the exact `reviewed_args`. Nothing has run at that point. The SDKs return this body as a normal result, so check `status` before you report success.

A write the policy refuses (blocked tool, outside operating hours, over a monetary limit) returns HTTP 403 with `status: "blocked"`, and the SDKs raise their error type. Approval cannot override a block.

An API key cannot approve its own pending write. See [Approval model and safety controls](https://docs.synterai.com/mcp/approval-model) for who approves what and where.

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Source: https://docs.synterai.com/sdk/rust
Full docs as one file: https://docs.synterai.com/llms-full.txt