Book a Sponsor MCP server for newsletter publishers: endpoint, tools, limits
For newsletter publishers and the agents they use: the Book a Sponsor MCP server is a free, public server at https://bookasponsor.com/mcp with four tools for newsletter sponsors and rates. It uses streamable HTTP and needs no key or sign-in. It returns brands, never people, from 8,550 brands in 4,988 newsletters, and median prices from 377 newsletters.
Every field and response below was read from the live server on 6 November 2026, protocol version 2025-03-26.
Book a Sponsor (bookasponsor.com) pitches brands to sponsor newsletters.
Quick picks: what are you doing?
| You want | Go to | Note |
|---|---|---|
| Claude or Claude Code | Connect Claude | A connector, or one command |
| ChatGPT or the OpenAI API | Connect ChatGPT | Depends on your plan |
| Another MCP client | The settings below | Remote server, streamable HTTP |
| To compare servers | Which tools have one | Who answers, and who needs a key |
What are the connection settings?
| Setting | Value |
|---|---|
| Endpoint | https://bookasponsor.com/mcp |
| Transport | Streamable HTTP (POST) |
| Authentication | None |
| Protocol version answered | 2025-03-26 |
| Server name it reports | sponsor-radar, from before the product was renamed |
| Tools | 4 |
Which tools does it have?
| Tool | Input | What it returns |
|---|---|---|
find_newsletter_sponsors | newsletter_url | Brands that sponsored newsletters like yours, with where and when their ads ran. Starts a scan if none exists: 15 to 60 seconds |
get_sponsor_scan | newsletter_url | Reads a scan back when the first call said it was still running |
list_brands_sponsoring_newsletters | niche (optional) | The brands seen in the most newsletters, overall or for one topic |
get_newsletter_sponsorship_rates | subscribers (optional) | The median printed price of a main slot by list size, with the middle half |
How do you test it from a terminal?
This call lists the rates. The response is cut to its first band and summary fields, read on 6 November 2026.
curl -s -X POST https://bookasponsor.com/mcp \
-H 'content-type: application/json' \
-H 'accept: application/json, text/event-stream' \
-d '{"jsonrpc":"2.0","id":1,"method":"tools/call",
"params":{"name":"get_newsletter_sponsorship_rates","arguments":{}}}'
{
"bands": [
{ "list_size": "Under 5,000", "newsletters": 79, "median_usd": 150 }
],
"newsletters_priced": 377,
"source_url": "https://bookasponsor.com/newsletter-sponsorship-rates"
}
The numbers are live, so a later call can differ from this page. At the top of the range, 100,000 or more lists at a median $1,200.
What does a scan's status mean?
| status | Meaning | What to do |
|---|---|---|
complete | Results are in | Read sponsors and open results_url |
running | The scan is working | Wait, then call get_sponsor_scan |
needs_details | It needs more about the newsletter | Open results_url |
refused | Blocked by the same rules as the website | Read message |
failed | The scan did not finish | Try again later |
What are the limits?
- It returns brands, never people: no buyer names, email addresses or drafted pitches come through this server.
- It can't send a pitch, sign you up, read your account or see your dash. The results link opens your run on bookasponsor.com.
- A scan lists the 8 closest fits, with the total count. The rest are on the results page.
- A new newsletter's scan can take up to a minute, and the same refusals as the website apply, such as adult content.
Questions
Is the server free?
Yes. There is no key, sign-in or card. It is the same data as the free pages on the site.
What authentication does it use?
None. It publishes no OAuth discovery, so choose no authentication in your client. A client that insists on OAuth will not connect.
Does a GET to /mcp work?
A browser gets a short info page. A plain JSON GET gets a 405, because the server takes POST requests. Our test client used POST for each call.
Where does the data come from?
Brands come from issues and sponsor pages Book a Sponsor reads, and rates from prices newsletters print on their advertise pages. The sponsors list and rates page explain the method.
Sources
- The live server, read 6 November 2026
- Model Context Protocol, read 6 November 2026
Have those brands pitched for you
Paste your newsletter. Book a Sponsor lists the brands that sponsored newsletters like yours, finds the person who buys the ads, and emails them every day from its own mailboxes. You get the replies and close the deal.
$1 card check gets 200 emails, then a plan from $19/mo · first sponsor reply inside 30 days or your money back