Let Agents In

Agent readiness · polar.sh

2026-08-12 10:07 UTC · formula v9.2 · 7.5s

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

https://polar.sh/signup loads turnstile. There is no version of that an agent solves.

10/ 16
A · Discovery
5/5
B · Agent entry
1/4
C · Registration
1/2
D · Provisioning
1/3
E · Integration
2/2

of the 16 points that apply to you and we could measure · 1 of 17 were not scored

You 10 · category median 9.5 · best stripe.com 11 · 15 deterministic HTTP checks, published formula

Pass it onEmail itLinkedIn

Fix this first

+5points, taking 10/16 to 15/16, past stripe.com

This is the whole list: everything we could measure and you do not pass. Another 1 point sits behind checks we could not evaluate on your domain, and each of those lines below says what would make it measurable.

  1. 1
    Agent entry pointan afternoon · +2

    Publish /agent-signup.md: the path from nothing to a working key, written as steps for a machine rather than a tour for a person. Ours is at /agent-signup.md if you want a worked example, and it says plainly that we have nothing to sign up for.

  2. 2
    Programmatic key provisioningan afternoon · +2

    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.

  3. 3
    No CAPTCHA in the signup HTMLan afternoon · +1

    Trigger turnstile 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.

Then, when you have room

  • 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.

Take it with you

5 of the checks an agent depends on, polar.sh 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 polar.sh. 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 polar.sh costs

Against payments and billing

You are 4 of 6 in a category where a developer is trying to take money without becoming a payments company.

  1. 1
    stripe.com
    11/16
  2. 2
    paddle.com
    9/14
  3. 3
    chargebee.com
    10/16
  4. 4
    polar.shyou
    10/16
  5. 5
    plaid.com
    9/15
  6. 6
    lemonsqueezy.com
    5/15

Where competitors pass and polar.sh does not

  • MCP surfacestripe.com · paddle.com · chargebee.com
  • Paths robots.txt points at answerstripe.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?
1/4
C
RegistrationCan an agent get an account?
1/2
D
ProvisioningCan it get credentials without a human?
1/3
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 and llms-full.txt present at https://polar.sh/llms.txt and https://polar.sh/llms-full.txt, and the 12 links we sampled across both files all answer
  • PASS
    Docs readable without JavaScript10,767 characters of text without JS, on https://polar.sh/docs/api-reference/oauth2/request-token rather than on https://polar.sh/docs/introduction
  • PASS
    On-demand agents not blockedExplicitly allowed: ChatGPT-User, Perplexity-User
  • 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

  • FAIL
    Agent entry pointNone of the 9 known agent entry paths returns a file rather than your page shellA markdown file written for a machine turns a guessing game into a procedure it can follow.
  • PASS
    OAuth dynamic client registrationregistration_endpoint published, but none of the 3 advertised grants (web, refresh_token, authorization_code) finishes without a person at a browser
  • FAIL
    MCP surfaceMCP mentioned 3x in your own files, but nothing answered at mcp.polar.sh, mcp.polar.sh/mcp, mcp.polar.sh/v1/mcp, api.polar.sh/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 HTMLturnstile appears in the signup page's server HTMLA CAPTCHA is a hard stop. Permissions after signup beat a gate before it.
  • PASS
    Signup reachable without a browserForm renders in server HTML at https://polar.sh/signup

D · Provisioning

  • FAIL
    Programmatic key provisioningNone of the 7 provisioning phrases appears in the 6 documents we readDocumented 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://polar.sh/resources/pricing: "Starter Free", "free Starter plan"

E · Integration

  • PASS
    Typed SDK on the registry@polar-sh/sdk@0.49.0 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://polar.sh/docs/introduction

What we discovered on the way

Docs
https://polar.sh/docs/introduction · linked from the site
Pricing
https://polar.sh/resources/pricing · linked from the site
Signup
https://polar.sh/signup · linked from the site
npm package
@polar-sh/sdk (registry guess)
GitHub
polarsource/polar
Package licence
MIT
Crawl-delay
none
Content-Signal
none
Blocked on-demand agents
none