# Customer.io — API Agent Score

> Score: 83/100 (Grade: A) | Domain: customer.io | Rubric: 1.0.0 | Checked: July 24, 2026

Customer.io scored 83/100 (A), classified "ai-ready".

[View full report](https://www.postman.com/ai/ai-ready-apis/company/customer)
[All organizations](https://www.postman.com/ai/ai-ready-apis/llms.txt)

## Summary

- Overall: 83/100 (A)
- Classification: ai-ready

## Category Scores

- API Design: 96/100 (A+)
- Developer Experience: 100/100 (A+)
- Agent Discovery: 93/100 (A+)
- Agent Understanding: 79/100 (B)
- Agent Usability: 59/100 (D)

## Check Results

### API Design

- [pass] Auth declared & discoverable — authentication documented in the docs site at https://docs.customer.io/messaging/channels/email/deliverability/authentication/. Investigated: spec 100%, docs 100%.
- [warn] Schema coverage & depth — 86/86 (100%) public params are fully typed (no any/**kwargs). Analyzer confirms all methods have a derivable input schema. Investigated: sdk 100%, spec 56%.
- [warn] Machine-readable, versioned contract — info.version="1.0.0" set but no versioning scheme (URL / header / media type) detected. Investigated: spec 81%, docs 63%.
- [pass] Security & governance hygiene — No credential-shaped strings detected in spec. Investigated: spec 100%, wellknown 0%.
- [pass] Example coverage — 34% example coverage. Investigated: spec 100%, docs 100%, sdk 100%.

### Developer Experience

- [pass] Self-service developer portal — Signup page at https://fly.customer.io/signup; no free-tier language detected in docs/pricing. Investigated: docs 100%.
- [pass] Quickstart present — Quickstart at https://docs.customer.io/integrations/data-in/connections/javascript/js-source/ has a runnable sample in the .md variant (https://docs.customer.io/integrations/data-in/connections/javascript/js-source.md). Investigated: docs 100%.
- [pass] Code samples in docs — Code samples present on 2/13 pages across 1 language(s); broader multi-language coverage missing. Investigated: docs 100%.
- [pass] Description completeness — 95% of operations + parameters have substantive descriptions. Investigated: spec 100%, sdk 80%.
- [pass] Changelog published — Newest official SDK activity 0 day(s) ago. Investigated: sdk 100%, spec 0%, docs 0%.

### Agent Discovery

- [pass] Docs reachable, not hard auth-gated — All 50 sampled pages are publicly accessible. Investigated: docs 100%.
- [pass] Registry & SDK presence — Indexed on Context7 (websites/customer_io, 4335 snippets). Investigated: docs 100%, cli 100%, sdk 92%.
- [warn] llms.txt present, valid & comprehensive — Same-origin links point to HTML and no markdown alternatives detected. Investigated: docs 75%, sdk 0%.
- [pass] Crawlable / AEO — Docs paths crawlable by all monitored AI agents. Investigated: wellknown 100%.

### Agent Understanding

- [pass] Machine-readable errors (RFC 9457) — No 4xx/5xx response codes (or default error response) documented anywhere in the spec. Investigated: docs 100%, spec 50%, sdk 50%.
- [pass] Operation purpose clarity — 100% of operations have a clear summary + operationId an agent can select on. Investigated: spec 100%.
- [warn] Agent-navigable, token-efficient docs — 5 of 49 pages have substantive content differences between markdown and HTML (avg 12% missing). Investigated: docs 75%.
- [fail] Agent instructions file (AGENTS.md) — No AGENTS.md at the site root or /.well-known/. Investigated: wellknown 0%.
- [fail] Docs structured data — Neither JSON-LD nor OpenGraph/meta tags detected across 1 assessed pages (1 JS-rendered). Investigated: docs 0%.
- [skip] Description consistency across surfaces — Only 1 surface description(s) with ≥6 tokens available; need at least 2 to compare.

### Agent Usability

- [pass] Idempotency documented — Built-in retry machinery is present (grep-derived). Investigated: sdk 100%, spec 0%, docs 0%.
- [pass] Sandbox separation — Sandbox environments are exposed (sandbox). Investigated: sdk 100%, spec 0%, docs 0%.
- [fail] Rate-limit signaling — No rate-limit response headers documented. Investigated: spec 0%, docs 0%.
- [fail] Pagination documented & consistent — 1 list endpoint(s) exist but no pagination params found. Investigated: spec 0%, docs 0%.
- [fail] Runnable collection with test scripts — No public Postman workspace discovered for the org. Investigated: platform 0%.

## Executive Summary

Customer.io's API program has a strong foundation in API design and documentation discovery, giving partners a reliable contract to build against. However, the program has two meaningful gaps that put partner integration quality at risk: agents and coding tools lack the structured context files and machine-readable signals they need to interpret and act on the API correctly, and partners have no runnable, test-backed collection to validate real workflows — compounded by missing rate-limit and pagination guidance that causes agents to build brittle integrations. Prioritize closing the agent context and runnability gaps first to ensure partners and their AI-assisted toolchains can self-serve end-to-end without support.