API Automation at the Pigeon Post Office

Hato API is your pigeon post office. Set delivery policies for your pigeon staff, write requests as Letters, connect them into Letterflows, and inspect results in your Letterbox.

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Core Architecture

Five simple concepts

Delivery Policy — Instructions for Your Pigeon Staff

A delivery policy defines how your pigeons send Letters: HTTP preferences, timeouts, retries, and size limits. Reuse the same policy across requests.

Configurable delivery behaviour: Timeout threshold, retry condition and number of attempts, request and response size, and more.
Protocol support: Able to send out HTTP1.1, HTTP2, HTTP3, FTP, and SFTP.
Reusable profiles: Share the same Delivery Policy configuration across multiple letters for easier management.

Learn about Delivery Policy →

Letter — A request component

Add a Letter component to a Letterflow. Choose its method, URL, headers, body, region, and Delivery Policy.

Request settings: Configure each request directly in the Letterflow builder.
Versatile delivery methods: Your pigeons can deliver Letters once, repeatedly, or on a schedule.
Send off location: Select the region where the letter should be dipatched from.

Learn about Letters →

Directory — Reusable Values for Your Letterflows

Share encrypted regional values, headers and credentials across Letterflows.

Reusable variables: Store text, secrets, JSON and XML once, then reference them in your Letterflows.
Shared request settings: Reuse headers, login credentials and private keys across your Letters.
Regional protection: Keep your values encrypted in the region you choose.

Learn about Directory →

Pigeon clerk consulting a Directory of shared values

Letterflow — Connected Deliveries and Data Processing

Chain multiple Letters, relay the data, manipulate and modify to desired outcome. Achieves simplifying your repeatable operation.

Draw on canvas: Drop any components into the canvas, connect them up, design your dataflow path.
Supports variable: Reference previous component data with double curly braces, and modify output by piping ( | ) to function.
Conditional branching: Route execution paths based on HTTP status codes or payload values dynamically.

Learn about Letterflows →

Letterbox — Place to store responses

Your central inbox where all delivery results are placed. Detail of the response is viewed here.

Data protection: Response will be stored to same region as where the letter got sent. Also the data is encrypted when it's at rest.
Intuitive response view: Easily identify which letter or component has ran, where's the request detail and response detail.
Pinning & retention policy: Response count and retention are limited. Pin important responses to preserve them.

Learn about the Letterbox →

How It Works

Sending request and viewing response in 3 steps

1 Configure & write

Create a Letterflow, add a Letter component, and choose its Delivery Policy.

2 Manual run or Schedule

Run your Letterflow on demand or attach a one-off or repeating Schedule.

3 Inspect in Letterbox

Watch responses arrive into Letterbox. Inspect response body, latency, status, and pin important responses.

Subscription & Plan

Simple plans, transparent limits.

Select the plan that fits your automated delivery Letterflow. Start free, scale as your needs grow.

Tax treatment depends on your location. Final currency, tax, and total are shown at checkout.

Plan comparison
Feature	Tinkerer USD 0 / forever	Aspiring USD 5 / mo	Description
Best for	For evaluation, hobby projects, and webhooks.	For active developers & production micro-jobs.	Choose the plan that fits your workload.
Letterflows	3	15	Saved Letterflows connecting one or more components.
Directory	5	30	Share encrypted regional values, headers and credentials across Letterflows.
Delivery Policies	1	5	Delivery profiles for protocols, timeouts, and retries.
Delivery / hour	12	180	Reachable outbound attempts, including redirects and retries, per rolling hour.
Letterflow emails / month	Unavailable	1000	Shared across flows and regions; resets on the first day at 00:00 UTC.
Letterflow emails / hour	Unavailable	20	Rolling hourly notification allowance, separate from request attempts.
Concurrent runs	1	3	One Letter or an entire Letterflow uses one slot.
Waiting deliveries	2	6	Wait for concurrency or hourly allowance; schedules opt in separately.
Minimum interval (minutes)	10	1	Shortest interval for repeated deliveries and cron schedules.
Letterflow regions	Single-region	Multi-region	Run within one region or coordinate across multiple regions.
API keys	1	3	Active API keys; available permissions depend on your plan.
API permissions	Read Letterbox Pin Letterbox entries Delete Letterbox entries	Read Letterbox Pin Letterbox entries Delete Letterbox entries Read Letterflows Run Letterflows Read run status Read Directory values, including secrets	Available permissions for explicitly scoped keys; account-specific limits may differ.
Retention (days)	14	60	How long execution content is kept; pinned entries do not expire.
Letterbox entries	10	80	Stored run results; the oldest unpinned entries are replaced at capacity.
Components excluding Start	6	15	Total components in each Letterflow.
Letter components	2	5	Maximum Letter components within one Letterflow.
Request body (MiB)	3	15	Maximum request body size per outbound attempt.
Response body (MiB)	3	20	Maximum response body size per outbound attempt.