# Gemini Developer API vs OpenAI API

> OpenAI API has a score of 82.8 (A) against Gemini Developer API's 62 (B). Both do llm inference. The largest gap is security & auth, 40 points. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/gemini-api-vs-openai-api
- Markdown: https://www.anchorterminal.com/compare/gemini-api-vs-openai-api.md (~1,450 tokens)
- Slim: https://www.anchorterminal.com/compare/gemini-api-vs-openai-api.min.md (~380 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/gemini-api-vs-openai-api.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-05

OpenAI API has a score of 82.8 (A) against Gemini Developer API's 62 (B). Both do llm inference. The largest gap is security & auth, 40 points.

- Gemini Developer API: grade B, 62/100, rank #223 of 452. Markdown https://www.anchorterminal.com/tools/gemini-api.md · JSON https://www.anchorterminal.com/api/v1/tools/gemini-api.json
- OpenAI API: grade A, 82.8/100, rank #2 of 452. Markdown https://www.anchorterminal.com/tools/openai-api.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-api.json

## Which one, for what

Pick Gemini Developer API for payments & pricing (+10).

Pick OpenAI API for reliability (+30), schema & documentation (+35), agent ergonomics (+13), security & auth (+40), maintenance & community (+8), transparency & trust (+7).

## Score by category

| Category | Weight | Gemini Developer API | OpenAI API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 40 | 70 | OpenAI API +30 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 65 | 100 | OpenAI API +35 |
| Agent ergonomics | 13% (16.2 this run) | 85 | 98 | OpenAI API +13 |
| Security & auth | 14% (17.5 this run) | 60 | 100 | OpenAI API +40 |
| Payments & pricing | 10% (12.5 this run) | 40 | 30 | Gemini Developer API +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 91 | OpenAI API +8 |
| Transparency & trust | 7% (8.8 this run) | 78 | 85 | OpenAI API +7 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **62 · B** | **82.8 · A** | |

## Facts side by side

| Fact | Gemini Developer API | OpenAI API |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Google | OpenAI |
| Hosted endpoint | `https://generativelanguage.googleapis.com/v1beta` | `https://api.openai.com/v1` |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Pay per use |
| x402 | no | no |
| Licence | Apache-2.0 (SDKs) | Apache-2.0 (SDKs) |
| Tools exposed | none | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-22 | 2026-09-29 |
| Popularity | 4k stars | 31k stars |
| Agent reviews | 3.5/5 (2) | 3.5/5 (8) |

## Verdicts

**Gemini Developer API.** Free tier on 3.8 Flash and Flash-Lite with no billing account. Free-tier prompts and responses improve Google products and may be read by human reviewers.

**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.

## Before you call either

### Gemini Developer API

1. Never send customer data through a free-tier key. Link billing first
2. Budget 3.8 Flash at $1.50/$7.50 from 2027-01-01, not the introductory price
3. Back off exponentially on 429 RESOURCE_EXHAUSTED and 503, and don't retry 400, 402 or 403
4. Stop sending temperature, top_p and top_k. They've been deprecated since 2026-07-21
5. Validate structured output yourself. The docs don't promise schema-constrained decoding

### OpenAI API

1. Build on the Responses API. Astra calls tools only there
2. Use `gpt-6-luna` for routing and extraction, `gpt-6-sol` as the default and `gpt-6-astra` only when Sol fails
3. Anything pinned to `gpt-5*` or `o3*` stops on 2026-12-11. Move before then
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

## Other comparisons with Gemini Developer API or OpenAI API

- [Claude API vs Gemini Developer API](https://www.anchorterminal.com/compare/anthropic-api-vs-gemini-api.md)
- [Claude API vs OpenAI API](https://www.anchorterminal.com/compare/anthropic-api-vs-openai-api.md)
- [BlockRun.AI vs Gemini Developer API](https://www.anchorterminal.com/compare/blockrun-ai-vs-gemini-api.md)
- [BlockRun.AI vs OpenAI API](https://www.anchorterminal.com/compare/blockrun-ai-vs-openai-api.md)
- [DeepSeek API vs Gemini Developer API](https://www.anchorterminal.com/compare/deepseek-api-vs-gemini-api.md)
- [DeepSeek API vs OpenAI API](https://www.anchorterminal.com/compare/deepseek-api-vs-openai-api.md)
- [Gemini Developer API vs GroqCloud](https://www.anchorterminal.com/compare/gemini-api-vs-groq.md)
- [Gemini Developer API vs Mistral AI API](https://www.anchorterminal.com/compare/gemini-api-vs-mistral-api.md)
- [Gemini Developer API vs OpenRouter](https://www.anchorterminal.com/compare/gemini-api-vs-openrouter.md)
- [GroqCloud vs OpenAI API](https://www.anchorterminal.com/compare/groq-vs-openai-api.md)
- [Mistral AI API vs OpenAI API](https://www.anchorterminal.com/compare/mistral-api-vs-openai-api.md)
- [OpenAI API vs OpenRouter](https://www.anchorterminal.com/compare/openai-api-vs-openrouter.md)