Your agent has no address.

An agent can call any API in the world and receive nothing back out of band. No OAuth redirect, no payment callback, no CI notification, no webhook. It runs on a laptop behind NAT, and the session ends before the callback lands.

Hookjar is an MCP server that hands your agent a public URL, holds whatever arrives, and lets it block until the callback shows up.

// add this endpoint to your MCP client
https://comiza.lighting/mcp

Free tier needs no account, no key and no signup.

Try it from this page

This runs against the live server, the same one your agent would use. The inbox below is real and belongs to your address for the next 24 hours.

Idle

Your URL, send anything to it

Install

Claude Code

claude mcp add --transport http hookjar \
  https://comiza.lighting/mcp

Any client, by config

{
  "mcpServers": {
    "hookjar": {
      "type": "streamable-http",
      "url": "https://comiza.lighting/mcp"
    }
  }
}

With a licence key

Pass the key as a bearer token and the Pro limits apply automatically.

{
  "mcpServers": {
    "hookjar": {
      "type": "streamable-http",
      "url": "https://comiza.lighting/mcp",
      "headers": { "Authorization": "Bearer YOUR_KEY" }
    }
  }
}

Six tools

Tool	What it does
`create_inbox`	Returns a public URL that captures any HTTP request sent to it.
`wait_for_request`	Blocks until something arrives, then returns it. Call this right after triggering the action that should call back.
`get_requests`	Lists what has arrived, without bodies.
`get_request`	Full method, headers, query and body of one request.
`list_inboxes`	Your inboxes and when they expire.
`delete_inbox`	Deletes an inbox and everything in it.

The shape of a session

1. create_inbox()                    -> https://comiza.lighting/h/a7f3
2. give that URL to Stripe, GitHub, your OAuth app, your CI
3. trigger whatever should call back
4. wait_for_request(inbox_id)        -> the request, headers and body

Limits

	Free	Pro
Active inboxes	1	25
Retention	24 hours	30 days
Requests per day	100	no cap
Body captured	64 KB	1 MB
Longest wait	60 s	300 s
Identified by	your address	licence key

Pro is $30 once, not a subscription. The free tier is not a trial and is not going away.

Get a licence key Instant delivery. Refunds handled by Payhip.

Things worth knowing before you rely on it

Anything sent to an inbox URL is readable by whoever owns that inbox.: On the free tier ownership is your network address, which is weak if you share an address with strangers. Do not point production webhooks carrying live secrets at it. It is built for testing, and that is what it should be used for.
Bodies are stored as inert bytes.: Nothing that arrives is parsed as code, executed, or used to build a command. Authorization and cookie headers are dropped on the way in rather than stored.
Inboxes expire, and expiry deletes.: 24 hours on free, 30 days on Pro. When an inbox expires its requests go with it. There is no archive.
One machine, one operator.: This runs on a single server in Germany. There is no cluster and no uptime guarantee. If that is not good enough for what you are building, it should not be in your critical path.