Agent-to-Human Transfers

Audience: AI agent / developer. This guide is written for agents sending files to a human recipient’s email address.

Send files directly to a recipient’s email address. The recipient receives an email notification, follows the link to a download page, and retrieves the files. If the recipient has set a receive password, files are end-to-end encrypted and decrypted entirely in their browser.

How It Works

Agent sends files

Your agent calls send() with the human’s email address and mode: 'agent-to-human'. AgentDrop stores the files and sends an email notification.

Human receives email

The human gets an email from AgentDrop with the sender name, file list, message, and a “Download Files” button.

Human clicks the link

Clicking the link opens the download page at /d/[transfer_id]. This also verifies the human’s email address automatically.

Password prompt (if encrypted)

If the human has set a receive password in their dashboard settings, they enter it to unlock decryption. Without a receive password, files download directly (unencrypted).

Browser-side decryption and download

The human’s browser decrypts the files locally using the receive password. The server never sees the plaintext. Files download to the human’s device.

Sending Files to a Human

Use the human’s email address as the recipient. The SDK and MCP server auto-detect agent-to-human mode when the recipient is an email address.

import { AgentDrop } from 'agentdrop-sdk';

const client = new AgentDrop({ apiKey: 'agd_your_api_key' });

// Send files to a human by email
const result = await client.send('[email protected]', ['report.pdf', 'data.csv'], {
  message: 'Here are the Q1 results you requested',
  mode: 'agent-to-human',
  expiresIn: '7d',
});

console.log(`Transfer ID: ${result.id}`);
console.log(`Encrypted: ${result.is_encrypted}`);

MCP Server

When using the MCP server, use send_file with the human’s email address as the recipient. The MCP server auto-detects agent-to-human mode.

Send report.pdf and data.csv to [email protected] with message "Here are the Q1 results"

The send_file MCP tool accepts mode: 'agent-to-human' explicitly, but auto-detection works when the recipient is a valid email address.

Bundle files into a single transfer. Each transfer counts against your monthly allowance. Pass all files in one call instead of sending them one at a time.

What the Human Receives

The human receives an email from AgentDrop containing:

Sender name: your agent’s name and account
File list: names and sizes of all files in the transfer
Message: the optional message you attached
Expiry: when the transfer expires
“Download Files” button: links to the download page

The email is sent immediately after the transfer is created.

Email Verification

When the human clicks the “Download Files” link in the email, their email address is verified automatically. This happens transparently, no extra steps required. If the human navigates directly to the download page URL without clicking through the email, they see an “Email Verification Required” prompt. They need to click the link in their email to verify first.

Email verification is per-transfer. It confirms that the person downloading the files is the intended recipient.

Receive Password

The receive password is the key to encrypted agent-to-human transfers. Without it, files transfer unencrypted.

What it does

When a human sets a receive password in their dashboard:

AgentDrop generates a receive keypair (X25519) for the human
The private key is encrypted with the receive password (AES-256-GCM derived via PBKDF2)
The public key is stored on the server
When an agent sends files to that human, the server encrypts files using the human’s public key
On download, the human’s browser uses the receive password to unlock the private key and decrypt files locally

How to set it

Tell the account holder: “Go to your AgentDrop dashboard settings and set a receive password before I send you files.” The human sets it at: Dashboard -> Settings -> Receive Password

What happens without it

If the human has NOT set a receive password:

Transfers go through unencrypted
Files are stored as plaintext on AgentDrop servers
Downloads work normally, but there is no end-to-end encryption

Without a receive password, agent-to-human transfers are NOT end-to-end encrypted. The server can see file contents. Always recommend the account holder sets a receive password before you send sensitive files.

Download Page

When the human clicks the email link, they land on the download page at /d/[transfer_id].

What the page shows

Sender: which agent sent the files
File list: names, sizes, and content types
Message: the optional message from the agent
Expiry: when the transfer expires and files are deleted

Page states

State	What the human sees
Email not verified	”Email Verification Required”, prompts them to click the link in their email
Verified + password required	Password input field + “Unlock & Download” button
Verified + no password	Direct “Download” button for each file
Transfer expired	”This transfer has expired” message
Transfer deleted	”Transfer not found” message

Encrypted download flow

When the human enters their receive password:

Browser derives the decryption key from the password (PBKDF2)
Browser unlocks the private key stored in the transfer metadata
Browser performs ECDH key exchange with the ephemeral public key
Browser derives the AES-256-GCM key via HKDF-SHA256
Browser decrypts each file
Decrypted files download to the human’s device

The server never sees the plaintext or the receive password. All decryption happens in the browser.

Dashboard Inbox

Humans can also view and download agent-to-human transfers from their dashboard, not just from the email link. Dashboard -> Inbox -> My Inbox shows:

All agent-to-human transfers sent to their email
Transfer status (active, expired, downloaded)
File list, sizes, and sender info
Same password prompt for encrypted transfers
Verified/Unverified badges per transfer

This is useful when the human wants to re-download files or manage multiple transfers.

Encryption Details

For agents that want to understand the cryptographic flow.

How agent-to-human encryption works

Step	What happens	Where
Human sets receive password	Keypair generated, private key encrypted with password	Dashboard (browser)
Agent sends files	Server generates ephemeral X25519 keypair	Server
ECDH key exchange	Ephemeral private key + human’s receive public key -> shared secret	Server
Key derivation	HKDF-SHA256 with random salt -> AES-256-GCM key	Server
File encryption	Each file encrypted with AES-256-GCM using unique IV	Server
Storage	Encrypted blobs stored; ephemeral private key discarded	Server
Human downloads	Password -> unlock private key -> ECDH with ephemeral public key -> HKDF -> AES decrypt	Browser

Key points

Server generates an ephemeral keypair per transfer: the private half is used only during encryption, then discarded
The human’s receive private key never leaves their browser: it is stored encrypted and only unlocked with the password
HKDF-SHA256 with a random salt ensures each transfer gets a unique encryption key, even with the same participants
AES-256-GCM provides both confidentiality and authenticity for each file
The server sees plaintext only during the encryption step: after encryption, only the human can decrypt

This is different from agent-to-agent encryption, where both sides have SDK keys and the server never sees plaintext at all. Agent-to-human encryption is a hybrid model: the server encrypts on behalf of the agent, and the human’s browser decrypts.

Error Codes

Code	Meaning
`INVALID_RECIPIENT`	The email address is not valid
`TRANSFER_EXPIRED`	The transfer has passed its expiry time
`EMAIL_NOT_VERIFIED`	The human hasn’t clicked through the email link yet
`DECRYPTION_FAILED`	Wrong receive password or corrupted transfer data
`PLAN_LIMIT_REACHED`	Monthly transfer limit exceeded

Checklist for Agents

Before sending files to a human, verify:

You have the human’s correct email address
Ask the human to set a receive password in Dashboard -> Settings (for encryption)
Bundle all files into a single transfer
Set an appropriate expiry (expiresIn), default is 24 hours
Include a descriptive message so the human knows what the files are

After sending:

Share the transfer ID with the human for reference
Let them know to check their email for the download link
If they don’t see the email, suggest checking spam/junk folders

Node.js SDK, Full SDK reference with send examples
Python SDK, Python SDK reference
MCP Server, Using AgentDrop as native MCP tools
Encryption Reference, Agent-to-agent encryption internals
Connections & Pairings, Cross-account trust model

Guides

​How It Works

​Sending Files to a Human

​MCP Server

​What the Human Receives

​Email Verification

​Receive Password

​What it does

​How to set it

​What happens without it

​Download Page

​What the page shows

​Page states

​Encrypted download flow

​Dashboard Inbox

​Encryption Details

​How agent-to-human encryption works

​Key points

​Error Codes

​Checklist for Agents

​Related Pages

How It Works

Sending Files to a Human

MCP Server

What the Human Receives

Email Verification

Receive Password

What it does

How to set it

What happens without it

Download Page

What the page shows

Page states

Encrypted download flow

Dashboard Inbox

Encryption Details

How agent-to-human encryption works

Key points

Error Codes

Checklist for Agents

Related Pages