Let Agents In

Agent readiness · mailgun.com

2026-08-12 10:05 UTC · formula v9.2 · 7.5s

A recaptcha challenge sits between an agent and an account it was ready to create.

https://signup.mailgun.com/new/signup loads recaptcha. There is no version of that an agent solves.

9/ 14
A · Discovery
5/5
B · Agent entry
0/2
C · Registration
0/2
D · Provisioning
2/3
E · Integration
2/2

of the 14 points that apply to you and we could measure · 3 of 17 were not scored

You 9 · category median 11.5 · best resend.com 14 · 15 deterministic HTTP checks, published formula

Pass it onEmail itLinkedIn

Fix this first

+2points, taking 9/14 to 11/14

This is the whole list: everything we could measure and you do not pass. Another 3 points sit behind checks we could not evaluate on your domain, and each of those lines below says what would make it measurable.

  1. 1
    No CAPTCHA in the signup HTMLan afternoon · +1

    Trigger recaptcha on a risk signal instead of on every signup, or open an API path to an account. A CAPTCHA is a hard stop, not a speed bump.

  2. 2
    Programmatic key provisioningan afternoon · +1

    Document how a key is created without opening a dashboard: management API, service account or CLI. If no such path exists, that gap is the finding, not the docs.

Then, when you have room

  • OAuth dynamic client registration a project · +1Publish OAuth authorization server metadata with an RFC 7591 registration_endpoint in it. It is the only standard way an agent registers itself without a human.
  • MCP surface a project · +1You already talk about MCP, and nothing answered at the addresses named above. If your server is at another path, declare it at /.well-known/mcp.json: that file is what an agent reads first, and it is what makes the path stop mattering.
  • Signup reachable without a browser a project · +1Let https://signup.mailgun.com/new/signup render its form in server HTML and stop refusing non-browser requests to it.

Take it with you

6 of the checks an agent depends on, mailgun.com does not pass.

Send yourself the list above with the checks that cost the most, and a permanent link. Whoever owns the fix is usually not the person who ran the scan.

One email with the report, and one follow-up asking what you did with it. No newsletter, no sequence. Delete on request at hello@letagentsin.com.

None of this tells you whether an agent picked you

Everything above is a file an agent could read. Whether one actually chose you is a different measurement, and we have not run it on mailgun.com. What we have run it on is a rich text editor vendor: six agents, one brief, six isolated copies of a real codebase. All six picked the same competitor, and the vendor being studied was never named, not even on a rejection list, while the runs named and dismissed ten alternatives between them. In an earlier round, run before we isolated the copies, it was named twice and struck off both times in four words: Fully commercial, licence key required. That study is about them, not about you. It is here because it is the difference between a file and a decision.

Read the audits in fullWhat the same run on mailgun.com costs

Against transactional email apis

You are 5 of 6 in a category where a developer is trying to send password resets and receipts that arrive.

  1. 1
    resend.com
    14/16
  2. 2
    loops.so
    13/16
  3. 3
    postmarkapp.com
    11/14
  4. 4
    sendlayer.com
    12/16
  5. 5
    mailgun.comyou
    9/14
  6. 6
    sendgrid.com
    9/14

Where competitors pass and mailgun.com does not

  • Signup reachable without a browserresend.com · postmarkapp.com · loops.so · sendlayer.com
  • MCP surfaceresend.com · loops.so · sendlayer.com
  • No CAPTCHA in the signup HTMLresend.com · loops.so · sendlayer.com
  • OAuth dynamic client registrationresend.com

Only domains we have actually scanned appear here, so the ranking is a floor: a competitor missing from the list has not been measured, not beaten.

By stage

A
DiscoveryCan an agent find and read you?
5/5
B
Agent entryIs there a door built for a machine?
0/2
C
RegistrationCan an agent get an account?
0/2
D
ProvisioningCan it get credentials without a human?
2/3
E
IntegrationCan it ship working code?
2/2

Every check

Each line is one HTTP observation with a published rule, so you can rerun any of them yourself. Most are the same tomorrow if you are: the two that are not are the bot gate and the pricing page, which answer inconsistently on their own, which is why those run more than once and say so when the tries disagreed. PASS and PART are counted. UNMEASURED means we could not evaluate it, N/A means it does not apply to a product like yours, and neither is in the score or its denominator. See the formula

A · Discovery

  • PASS
    Answers an agent user-agentAnswered 200 to LetAgentsIn/1.0 (+https://letagentsin.com/methodology)
  • PASS
    llms.txt publishedllms.txt present at https://documentation.mailgun.com/llms.txt, and the 12 links we sampled across the file all answer
  • PASS
    Docs readable without JavaScript10,570 characters of text without JS, on https://documentation.mailgun.com/docs/mailgun/user-manual/api-key-mgmt/rbac-mgmt rather than on https://documentation.mailgun.com/docs/mailgun/sdk/introduction
  • PASS
    On-demand agents not blockedNo on-demand agent is blocked
  • N/A
    Paths robots.txt points at answerrobots.txt names no concrete path, only patterns or nothing, so there is no claim to check
  • PASS
    No punishing crawl delayNo Crawl-delay applies to the agents we check

B · Agent entry

  • UNMEASURED
    Agent entry pointUnmeasurable: 8 of the 9 known agent entry paths answered with a refusal rather than a file or a 404, so what you publish there is not something we measuredLet ordinary HTTP reach these paths and this becomes measurable.
  • FAIL
    OAuth dynamic client registrationNo OAuth metadata on any of the 9 hosts probed, including the usual auth and api subdomainsRFC 7591 is the only standard path by which an agent can register itself without a human.
  • FAIL
    MCP surfaceMCP mentioned 2x in your own files, but nothing answered at mcp.mailgun.com, mcp.mailgun.com/mcp, mcp.mailgun.com/v1/mcp, api.mailgun.com/mcp, /mcp or /api/mcpAn MCP server turns your API from something an agent reads about into something it can call.

C · Registration

  • FAIL
    No CAPTCHA in the signup HTMLrecaptcha appears in the signup page's server HTML, even though the form itself is assembled by JavaScriptA CAPTCHA is a hard stop. Permissions after signup beat a gate before it.
  • FAIL
    Signup reachable without a browserhttps://signup.mailgun.com/new/signup is reachable, but its form needs JavaScriptIf a bare HTTP request gets a 403, the agent never sees the form at all.

D · Provisioning

  • PART
    Programmatic key provisioning1 of 7 provisioning phrases across the 5 documents we read: "account api"Documented key creation is the difference between a two-minute integration and a support ticket.
  • PASS
    Free tier or no-card trial stated in textFree tier or no-card signals at https://www.mailgun.com/pricing/: "Free plan", "free trial", "Try for free"

E · Integration

  • PASS
    Typed SDK on the registrymailgun.js@14.0.0 ships types, matched from the registry by who publishes it rather than by a link on your site
  • PASS
    Machine-readable API descriptionDocs serve markdown to machines, at https://documentation.mailgun.com/docs/mailgun/sdk/introduction.md

What we discovered on the way

Docs
https://documentation.mailgun.com/docs/mailgun/sdk/introduction · linked from the site
Pricing
https://www.mailgun.com/pricing/ · linked from the site
Signup
https://signup.mailgun.com/new/signup · linked from the site
npm package
mailgun.js (registry guess)
GitHub
not found
Package licence
MIT
Crawl-delay
none
Content-Signal
none
Blocked on-demand agents
none