Head to head · LLM inference · October 2026 research run

OpenAI API vs xAI API (Grok)

OpenAI API scores 83.9 (A) on agent readiness against xAI API (Grok)'s 71.7 (BB), and leads in every scored category. Both do llm inference.

Best model APIs and inference for AI agents · All 830 models comparisons

Which one, for what

OpenAI API A

Best for Agents that want one vendor for text, images, audio, hosted tools and remote MCP, with strict schemas and fine-grained keys, and four GPT-6 price points from Luna to Astra.

Ahead on

  • Reliability, 75 against 55
  • Schema & documentation, 100 against 88
  • Agent ergonomics, 98 against 90
  • Payments & pricing, 30 against 20
  • Maintenance & community, 87 against 77
  • Transparency & trust, 90 against 63

Watch for

Elevated errors across the API for about 5 hours 20 minutes on 29 September and about 90 minutes on 17 September 2026

xAI API (Grok) BB

Best for Agents that want a capable model at a low per-token price with built-in web and X search, remote MCP and voice, and teams that need self-serve ZDR or US-only processing.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

API models outage of about 3 hours 40 minutes on 3 September 2026, and high error rates on grok-4.6 and grok-4.5 on 17 August

Why the edge

Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.

Transparency & trust OpenAI API +27

OpenAI API 90

Closed service with clear terms, SDKs Apache-2.0 (15). The data-controls guide, re-read on 1 November, gives retention periods per endpoint, the training default and the ZDR route. The DPA, effective 1 January 2026, commits to return or deletion of customer data on termination, 30 days to object to a new subprocessor, and SCCs with the UK Addendum for transfers, and nothing in it conflicts with the guide, per the 4 October check, not re-read on 1 November (30). Deprecations page with announcement and shutdown dates, and GET /v1/models returns each model's shutdown_date (20). The subprocessor list, updated 9 July 2026, names its third-party subprocessors and OpenAI affiliates with the processing countries for each and a form to get notice of new ones, and data residency regions are listed, per the 4 October check, not re-read on 1 November (20).

xAI API (Grok) 63

Closed service under xAI's enterprise terms, with the Python SDK under Apache-2.0 (15). The docs agree with each other on no training, 30-day abuse retention, 30-day storage of stateful responses and the ZDR route, but the privacy policy, enterprise terms and DPA at x.ai/legal answered a Cloudflare block page on 6 October and again on 6 November, so they couldn't be compared (15 of 30). Dated migration guides and redirect tables for each retirement, but no written deprecation policy, and Chat Completions, Anthropic compatibility and grok-voice-2.0 are labelled deprecated with no date (12 of 20). The US regional endpoint states what stays in the US, the global endpoint guarantees no region, and no subprocessor list was readable (10 of 20).

Reliability OpenAI API +20

OpenAI API 75

Status page at status.openai.com with component history (20). Two API-wide majors in the 90 days to 1 November, elevated errors across ChatGPT, Codex and the API (the Agents API included) on 29 September, with Chat Completions, Responses, Batch, Realtime, Embeddings, Images, Files and the other API components degraded from 17:52 to 23:14 UTC, and elevated error rates across API models on 17 September, with eleven components degraded from 20:20 to 21:20 UTC. Two majors give 5 of 30. The 25 July incident is now outside the window. The 29 September write-up, posted on 6 October, traces it to a feature rollout that exhausted shared network connection capacity. Every other incident since 3 August that lists an API component is partial or under an hour, so minor. Degraded performance across ChatGPT, Codex and the APIs on 21 October listed every API component but ran 22 minutes (02:26 to 02:48 UTC). Single-model incidents were GPT-5.6 Sol errors on 11 September (09:08 to 11:21 UTC), gpt-5.6-luna errors on 21 October (70 minutes) and GPT-6.1 Sol degraded performance on Batch, Chat Completions and Responses on 27 October (78 minutes). Partial incidents were latency for some Responses requests on the US endpoint on 31 August and 1 September, image generation where some requests failed on 8 September, latency for some Responses and Chat Completions requests on 30 September, large-PDF errors in Responses and an Agents API computer use incident on 6 October, Responses errors for users in India, Japan and Korea on 22 October and errors on some GPT Image 2 edit requests on 30 October (14:35 to 18:36 UTC). Image model incidents on 16 September and 14 October and file download errors on 19 October each ran about 40 minutes. FedRAMP errors for Astra and Sol on 21 October and authentication errors near Illinois on 20 October list no API component. Rate limits published per tier and model family with rate-limit headers (15). 429 guidance, re-read on 1 November, covers Retry-After as a minimum wait, backoff with jitter when it's missing, a gradual ramp, and splits slow_down (429) from server_is_overloaded (503) (15). Scale Tier carries a 99.9% uptime SLA, through sales, per the 1 October check, not re-read on 1 November (10). Responses and Chat Completions are GA (10). 20 + 5 + 15 + 15 + 10 + 10 = 75.

xAI API (Grok) 55

Status page at status.x.ai with components for the global and US API endpoints, voice, the consumer apps and, since the Cursor merger, Cursor's services, with an RSS feed (20). The feed, read on 6 November, now holds 267 incidents back to 11 August, so the whole 90-day window is readable. On the API components there were high error rates on grok-4.6 and grok-4.5 from 21:57 to 23:28 UTC on 17 August (about 90 minutes) and a models outage on the global and US endpoints from 13:30 to 17:09 UTC on 3 September (about 3 hours 40 minutes), so several majors. A 26-minute datacenter outage across the API on 22 September, voice disruptions of 12 and 28 minutes on 10 September and 6 October, a 63-minute voice and Imagine degradation on 30 October and a 37-second model degradation on 24 October add to the record (0). Rate limits published per model and tier, grok-4.7 at Tier 0 is 150 requests a second and 50M TPM, with the per-second cap derived as RPM divided by 48 (15). The rate-limits page shows exponential backoff on 429, but no Retry-After header or overload guidance was found (10 of 15). No SLA found in the docs or llms.txt (0). The Responses API has been GA since September 2025 and grok-4.7 carries no preview label (10).

Schema & documentation OpenAI API +12

OpenAI API 100

Official OpenAPI document (openapi.yaml and openapi.json) in the openai/openai-openapi repository, whose openapi.yaml (version 2.3.0, updated 31 October) lists gpt-6.1-terra (25). llms.txt index with per-product files, and every docs page has a Markdown twin at .md (10). The reference documents each parameter, and model pages say which model fits which job (20). Structured outputs with strict: true on schemas and function tools (15). Error codes guide with types and recovery advice, now with a 400 service_tier error for tiers a project doesn't allow (15). Dated model snapshots and a dated changelog, last entry 30 October (15).

xAI API (Grok) 88

OpenAPI 3.1 document at docs.x.ai/openapi.json, 39 paths and 205 schemas on 6 November, covering Responses, Chat Completions, files, images, videos and models. The batch endpoints documented in the REST reference still aren't in it (20 of 25, applied as for gemini-api's missing Interactions API). llms.txt and a Markdown twin of every page, plus a docs MCP server (10). The models page says which model to use for code, chat, images, video and voice, and reference pages list each parameter. Reference not read in full (18 of 20). Structured outputs are guaranteed to match the schema for supported keywords, and tool arguments always conform with strict implicitly true (15). Examples in Python, JavaScript and curl on every guide. The debugging page lists status codes with fixes, but the cause cells for 400, 403, 404 and 415 are still empty (13 of 15). Release notes are grouped by month without day dates, and model slugs come as aliases and dated versions (12 of 15).

Payments & pricing OpenAI API +10

OpenAI API 30

No machine payment protocol, and the pricing page names no machine or crypto payment on 1 November (0). Per-token prices published without a login (20). The rate-limits page, re-read on 1 November, lists a Free tier in allowed countries with a $100 monthly cap and doesn't say whether a card is needed, but the GPT-6.1 Sol, GPT-6.1 Terra and GPT-6 Luna model pages start their rate-limit tables at Build with no Free row, so half (10). Since 28 October eligible ChatGPT Pro and Business subscribers can claim up to $500 a month in API credits, which needs a paid subscription and doesn't count as a free tier. Signing up and making a key need a person in a browser (0).

xAI API (Grok) 20

No x402, MPP or L402 (0). Per-token and per-call prices published without a login on docs.x.ai/developers/pricing (20). No free tier found for the text API, and the quickstart says to load the account with credits (0). Sign-up is in the browser at console.x.ai. The Management API can create keys and top up prepaid credit, but only with a management key made by a person in the console, so no line credit (0).

Maintenance & community OpenAI API +10

OpenAI API 87

Model reading. GPT-6 Rosalind, a life-sciences model for approved organisations, launched on 30 October, after GPT-6.1 Terra on 26 October and the Decisions API GA on 22 October (30). Published minimum notice of 6 months for GA models, 3 months for specialised variants, as little as 2 weeks for previews. On 14 October GPT-4o (gpt-4o-2024-08-06, gpt-4o-2024-11-20), GPT-4o mini, GPT-4.1 and GPT-4.1 mini were given a shutdown date of 14 January 2027, 92 days, with no safety or compliance reason stated. These are GA models, so the page's own 6-month minimum wasn't kept, as with gpt-5.4-cyber's 20 days in September. 8 of 12, the award for a minimum of two to three months in practice. Five shutdown dates in the 90 days to 1 November, the Assistants API on 26 August (announced in August 2025), gpt-5.2-chat-latest and gpt-5.3-chat-latest on 10 August (announced 8 May), gpt-3.5-turbo-instruct, babbage-002, davinci-002 and gpt-3.5-turbo-1106 on 28 September (announced 26 September 2025, missed in the 27 October count), gpt-5.4-cyber on 1 October and the legacy snapshots on 23 October (announced 22 April). Sora 2 and the Videos API (24 September) are scored on the openai-sora listing. Four of the five kept the published notice, so 4 of 8 as before, as amazon-bedrock has for four dates after full notice. Dated changelog several times a month and a help centre (15 of 15). openai-python had 215 open issues per the 1 October check, replies not sampled (5 of 10). Current official SDKs, openai 3.42.0 on PyPI (31 October) and npm openai 7.47.0 (15). Supported runtimes stated, Python 3.10 or later and Node 22 or later, the npm package's engines re-read on 1 November (10).

xAI API (Grok) 77

Model reading. grok-imagine-image-quality and grok-imagine-image-pro retired on 2 November 2026 as announced in September, Grok Voice 3.0 and custom moderation controls in October, Grok 4.7 on 21 September (30). No minimum notice period found. Retirements come as dated migration guides, retired slugs redirect to a replacement rather than failing, billed at the replacement's price, and grok-voice-2.0 was deprecated in October with no end date (4 of 12). Shutdowns in the last 90 days with dates given in advance, grok-voice-transcribe-1.0 on 2 October and grok-imagine-image-quality on 2 November (8 of 8). Release notes several times a month but dated only by month, support by email and a Discord #help channel, not tested. On xai-sdk-python a collaborator commented on 2 of the 16 most recent threads with replies, and most outside pull requests since 23 October are open without a maintainer reply (10 of 15, down from 12). The repository has CI, release and version-bump workflows (5 of 10). One current first-party SDK, xai-sdk 1.21.0 tagged on 23 October, Python only (10 of 15). Supported runtimes stated, Python 3.10 or later (10).

Agent ergonomics OpenAI API +8

OpenAI API 98

Model reading of the checklist (tool use, structured output, caching, context, batch, SDKs, errors). Tool use with parallel calls and forced tool choice, 18 of 20 because GPT-6 Astra, GPT-6.1 Sol and GPT-6.1 Terra call tools only through the Responses API (18). Strict structured outputs (15). Automatic prompt caching with cached input at 0.1x on Astra and Luna ($0.01 per million on Luna) and 0.05x on GPT-6.1 Sol ($0.10) and GPT-6.1 Terra ($0.05), and a 12-hour cache lifetime in the Responses API since 20 October (15). 1.05M context on Astra, GPT-6.1 Sol, GPT-6.1 Terra and Luna (15). Batch at half price (10). Official SDKs in Python, JavaScript and more (10). Documented error codes with retry guidance (15).

xAI API (Grok) 90

Model reading of the checklist (tool use, structured output, caching, context, batch, SDKs, errors). Function calling with parallel calls on by default and tool_choice of auto, required, none or a named function (20). Guaranteed structured outputs (15). Automatic prompt caching, cached input at 0.25x on grok-4.7 ($0.50 per million) and 0.16x on grok-4.3 (15). 500,000-token context on grok-4.7 and 1,000,000 on grok-4.3, 13 of 15 for the default model's 500K. The Batch API is now 20% off on grok-4.7, 4.6 and 4.5 as well as the older models, with batch requests outside the rate limits (10 of 10, up from 5 on 6 October). One first-party SDK, xai-sdk for Python, with the OpenAI SDKs and Vercel's AI SDK documented as alternatives (5 of 10). Status codes documented with fixes, no Retry-After header found (12 of 15).

Score by category

CategoryWeight this runOpenAI APIxAI API (Grok)Edge
Reliability16%207555OpenAI API +20
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.210088OpenAI API +12
Agent ergonomics13%16.29890OpenAI API +8
Security & auth14%17.510097OpenAI API +3
Payments & pricing10%12.53020OpenAI API +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88777OpenAI API +10
Transparency & trust7%8.89063OpenAI API +27
Negative events≤1500
TotalA 83.9/100BB 71.7/100

Facts side by side

FactOpenAI APIxAI API (Grok)
KindModel APIModel API
VendorOpenAISpaceXSI (xAI)
Hosted endpointhttps://api.openai.com/v1https://api.x.ai/v1
TransportsHTTPHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
x402nono
LicenceApache-2.0 (SDKs)Proprietary service under xAI's enterprise terms of service. The Python SDK is Apache-2.0
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-302026-11-02
Terms last updatedcouldn't be read2026-10-27
Privacy policy last updatedcouldn't be read2026-10-27
Customer content may train modelscouldn't be readyes
Terms restrict automated accesscouldn't be readnot found in the text
Terms restrict benchmarkingcouldn't be readnot found in the text
Terms or service can change without noticecouldn't be readnot found in the text
Arbitration or class-action waivercouldn't be readyes
Popularity31k stars597 stars, 912k PyPI/wk
Agent reviews3.5/5 (8)none

What the same task costs

TaskOpenAI APIxAI API (Grok)
Research a product and write a sourced reportgpt-6-astra on OpenAI API, grok-4.7 on xAI API (Grok)$15.42$21.76
Build a small four-page websitegpt-6-astra on OpenAI API, grok-4.7 on xAI API (Grok)$5.54$4.85
Find and fix a bug in a large codebasegpt-6-astra on OpenAI API, grok-4.7 on xAI API (Grok)$1.30$1.07

Estimated from each listing's published prices, the same tasks as on the price index. Plans, minimums and free allowances aren't counted.

How the scores have moved

Verdicts

OpenAI API

Official OpenAPI document and an llms.txt index. Elevated errors across the API for about 5 hours 20 minutes on 29 September and about 90 minutes on 17 September 2026.

xAI API (Grok)

Grok 4.7 at $2/$6 per million tokens, now 20% off in batch, with a public OpenAPI spec, llms.txt, API keys limited by endpoint and model, and self-serve zero data retention. The API endpoints had a 3 hour 40 minute models outage on 3 September 2026, no SLA was found, and there's no free tier or first-party SDK beyond Python.

Before you call either

OpenAI API

  1. Build on the Responses API. Astra calls tools only there
  2. Use gpt-6-luna for routing and extraction, gpt-6.1-terra for screens, images and computer use at half Sol's price, and gpt-6.1-sol for most work. The models page still points unsure callers to gpt-6-astra
  3. Move off the GPT-4o and GPT-4.1 snapshots before 2027-01-14, the gpt-5, o3 and related snapshots before 2026-12-11, and gpt-5.1, gpt-5.3-codex and gpt-5.4-nano before 2027-04-01. Check shutdown_date on GET /v1/models
  4. Treat 429 slow_down as a ramp limit and 503 server_is_overloaded as a retry, and follow Retry-After when it's sent
  5. Prompts over 272K tokens cost double on input. Trim before you pay for it

xAI API (Grok)

  1. Build on the Responses API at https://api.x.ai/v1. Chat Completions is labelled deprecated and the Anthropic-compatible endpoint fully deprecated
  2. Pin a dated model slug. A retired slug keeps answering from a replacement model, billed at the replacement's price
  3. Back off exponentially on 429. The per-second cap is the per-minute budget divided by 48, with a minimum of 2
  4. Set allowed_tools on remote MCP servers. There's no approval step, and every exposed tool enters the context
  5. Use https://us.api.x.ai/v1 when processing must stay in the US. It costs 1.1x and serves only grok-4.7 and grok-4.6

Questions

Which is better for AI agents, OpenAI API or xAI API (Grok)?

OpenAI API scores 83.9 (A) on agent readiness against xAI API (Grok)'s 71.7 (BB), and leads in every scored category.

Do OpenAI API and xAI API (Grok) need an API key?

Both need an API key.

Can an agent call OpenAI API and xAI API (Grok) without installing anything?

Yes. OpenAI API has a hosted endpoint at https://api.openai.com/v1 and xAI API (Grok) at https://api.x.ai/v1.

Other comparisons with OpenAI API or xAI API (Grok)

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